Gender and leadership? Leadership and gender? A journey through the landscape of theories

نویسندگان

  • Steven H. Appelbaum
  • John Molson
  • Lynda Audet
  • Joanne C. Miller
  • Egon Zehnder
چکیده

The purpose of this article was to examine the following three questions: Are women’s leadership styles truly different from men’s? Are these styles less likely to be effective? Is the determination of women’s effectiveness as a leaders fact-based or a perception that has become a reality? Conclusions revealed: Question one: Yes, women’s leadership style is, at this point, different from men’s but men can learn from and adopt `̀ women’s’’ style and use it effectively as well. In other words, effective leadership is not the exclusive domain of either gender and both can learn from the other. Question two: No, women’s styles are not at all likely to be less effective; in fact, they are more effective within the context of team-based, consensually driven organizational structures that are more prevalent in today’s world. Question three: The assessment that a woman’s leadership style is less effective than a man’s is not fact-based but rather driven, by socialization, to a perception that certainly persists. The inescapable reality is that, within the senior ranks of corporate north America (and elsewhere), women remain conspicuous by their absence. Received: February 2002 Revised: August 2002 Accepted: September 2002 in 1992, only 2% of those CEO’s considered it likely that their company would have a female CEO within the next decade’’ (Oakley, 2000; Fischer, 1992). The Catalyst organization (an American non-profit organization devoted to the advancement of women in business) is more optimistic and projects the percentage of women corporate officers in future years to be 16.5 percent in 2005, 20.1 percent in 2010 and 27.4 percent in 2020. Even if predictions prove true, underrepresentation will remain notable despite these increases. The landscape of theoretical approach Research has produced various theories: whether or not the approach to leadership differs between men and women as distinctive biological groups; whether this difference is one of style or substance; whether it is real or perceived; whether one leadership approach is more or less effective than the other and which is more likely to lead to success. Four schools of thought will be examined here: 1 biology and sex; 2 gender role; 3 causal factors; 4 attitudinal drivers. These issues are considered from the perspective of the male and female leaders themselves, their peers, their supervisors and their subordinates. The first theory seems to be based on the premise that leadership is biologically determined, innate for men and therefore unattainable for women. A second approach acknowledges the role of socialization and explores the notion of gender role as a determinant of leadership. A third perspective involves the identification and consideration of a variety of other contributing factors ± prevailing attitudes, women’s self-confidence, their prior experience, the corporate environment, and the old boys’ network ± that could predict or influence leader emergence. Emergent thinking accepts that there may well be a difference in the way men and women approach leadership and then attempts to capture or articulate this difference in terms of real world implications. Within this context, it has even been suggested that a female approach could have an advantage in flatter, more global organizations. This is being examined and tested in contemporary research in HRM and organization behavior studies. Biology and sex The basic premise of this body of research is that leadership is biologically determined, behaviorally demonstrated and innate to the male species. As such, an effective leadership stance can only be assumed by the male species. Much of the supporting work restricts leadership studies to male subjects. The premise for biological sex =male = leader does seem somewhat biased. In fact, an unstated premise of this biologically driven approach may have been that women could attain a position of leadership just as easily as they could become men. Perhaps not surprisingly, research results do not substantiate this approach and pursuit of this direction is limited. While a few studies have found gender differences in leadership style (Helgesen, 1990; Hennig and Jardim, 1977; Rosner, 1990), most research points to their absence (Bass, 1990; Dobbins and Platz, 1986; Donnell and Hall, 1980; Maccoby and Jacklin, 1974). With the argument that men and women are biologically different in terms of leadership being difficult to support, researchers are investigating another direction: not only are men and women similar, women may be equally effective. Kolb (1999) and Shimanoff and Jenkins (1991) demonstrate in their research that there are far more similarities than differences in the leadership behaviors of men and women, and they are equally effective. As such, with few findings lending Table I Percentage point increase Period F500 corporate officers +3.8 1995 vs 2000 F500 board of directors +2.2 1995 vs 2000 F500 corporate line officers +2 1997 vs 2000 Highest ranking corporate +2.7 1995 vs 1999 Officer positions F500 top earners +2.9 1995 vs 2000 Source: Catalyst (2001) [ 44 ] Steven H. Appelbaum, Lynda Audet and Joanne C. Miller Gender and leadership? Leadership and gender? A journey through the landscape of theories Leadership & Organization Development Journal 24/1 [2003] 43-51 credence to biological sex as a valid research hypothesis to differentiate male versus female leadership, the biological sex approach gives way to broader studies. Interestingly, though learning is evolving, the thinking behind the biological approach appears to linger. Despite the fact that many researchers have found that there are few differences in the innate abilities of male and female managers (Oakley, 2000; Dobbins and Platz, 1986; Powell, 1993), stereotypes persist that portray women as less capable leaders than men. Gender role This second area of exploratory work regarding male versus female leadership is likely inspired by two factors: 1 biological sex proving an unlikely determinant of the different leadership styles; and 2 persistent beliefs that differences in male versus female leadership do indeed exist and the consequent view that other, different determinants of leader effectiveness must also exist. Related research expands upon the idea that an individual’s gender is linked solely to the person and moves on to the more general concept of gender role with the purpose of linking leadership effectiveness or leadership emergence to characteristics or behaviors thought to be typically male or female. The various results can be typified very simply as follows: gender role is a better predictor of leader emergence than sex (Kent and Moss, 1994). Curiously, a new dimension to gender role surfaces: there are three, not two, genders in the mix of variables: male, female and androgynous. It is interesting to reflect on what results related to androgyny might mean. Stereotypical masculine behaviors are still considered important for leadership. Individuals who reported that they exhibited these behaviors without the accompanying more supportive (feminine) behaviors were viewed as leaders in a higher percentage than any other category originally defined. However, in terms of androgynous behaviors it may be the balance of behaviors, rather than a high amount of both behaviors, that becomes important (Kolb, 1999). Clearly, from a woman’s perspective, the merits of androgyny show potential. Although masculinity still appears to have a significant relationship with leader emergence, a possible relationship between androgyny and leader emergence indicates that the possession of feminine characteristics, in balance with masculine ones, also may be important in perceptions of leadership (Kolb, 1997). Individuals with masculine or androgynous classifications are more likely to be identified as preferred leaders than individuals with undifferentiated or feminine scores (Kolb, 1999). As such, a component of this second line of thought suggests a leadership style more appropriate and more promising for women (Kent and Moss, 1994). Contrary to previous findings that identify `̀ female deficiencies’’ as a reason why few women have made it to the top, the emergence of androgynous leaders suggests that the possession of feminine characteristics does not decrease an individual’s chances of emerging as a leader as long as the individual also possesses masculine characteristics. If women are more likely to be androgynous, they may have a better chance of rising to leadership status. Other findings have indicated that following a masculine model has both advantages and disadvantages for aspiring women managers. Developmental differences between both sexes have helped to explain some of the problems for leaders and followers. Interactive leadership styles utilized by women have been beneficial in moving both genders towards a solution in so far as this style involves four factors: encouraging participation; sharing power and information; enhancing self-worth of others and finally, energizing others. The use of an androgynous leadership model has not yielded significant findings but there are common characteristics of successful leaders combining both the masculine and feminine models. Organizations and their top leaders need to expand their definition of effective leadership so that an interactive style can be valued, allowing these organizations the necessary flexibility, key to surviving within an increasingly competitive and diverse environment (Appelbaum and Shapiro, 1993). The gender role concept of leadership and the provision of a style alternative helps solve a dilemma for women. `̀ A double bind that is particularly troublesome for women leaders is what Jamieson calls the feminine/ competency bind, where acting `feminine’ is associated with incompetence, and acting `competent’ is associated with the opposite polarity of masculine traits that when adopted by women can only lead to the conclusion that one must be `un-feminine’ to be competent’’ (Oakley, 2000; Jamieson, 1995). However, women are less likely to be preselected as leaders and the same leadership behavior is often evaluated more positively when attributed to a male than a female (Kolb, 1997). [ 45 ] Steven H. Appelbaum, Lynda Audet and Joanne C. Miller Gender and leadership? Leadership and gender? A journey through the landscape of theories Leadership & Organization Development Journal 24/1 [2003] 43-51 A better definition of androgyny may be required. Does it refer to a good balance of male and female behaviors? Does that mean that an individual would have to score high on both scales or does a low score on both scales also qualify as androgyny? Is a new scale required? In fact, a totally new scale, redefining each variable, may be required since it appears that much of gender role research traces back to Bem’s (1974) definition of stereotypical gender characteristics. This work may no longer be applicable to more current socializations of gender role. In terms of gender role, Kolb (1999) notes that there is no difference between males and females on scores on the masculinity scale. Apparently, traits and behaviors identified as masculine in Bem’s historical (1974) study have been adopted by both sexes. This would conform to current thinking which suggests that it is not reasonable to judge a quality such as sensitivity as exclusively female or assertiveness as exclusively male. An outcome of gender role research is the identification of a multiplicity of possible factors beyond gender or gender role that contribute to perceptions of leadership. Environmental factors A thorough exploration of all the factors contributing to leadership effectiveness or leadership emergence and the implications of these factors in terms of evaluating real or perceived male versus female differences would clearly be beyond the scope of this review. What follows, instead, is a sampling of selected causal factors, presented to give the reader some appreciation of the complexity of the issues and componentissues. More importantly, it is believed that what may have started as a very simple question and answer (Q: do men or women make better leaders? A: men are better leaders because biology made them so) quickly grew in complexity. The consideration of causal factors does provide some insight into this complexity. Selected factors that potentially undermine a woman’s leadership effectiveness include: women’s attitude, women’s self-confidence, women’s prior work experience, the corporate environment, and the old boys’ network. Women’s attitude Attitude toward leadership is a stronger predictor of leader emergence than masculinity (Kolb, 1999) but women may be at a disadvantage because the more docile, unleader-like impression they have been socialized to give sends a message of incompetence (Claes, 1999; Lipsey et al., 1990): According to the sex role theory, being a man or a women means enacting a general role as a function of one’s sex. But this theory also uses the words masculine and feminine, asserting that the feminine character in particular is produced by socialization into the female role. According to this approach, women acquire a great deal of sex role learning early in their lives, and this can lead to an attitude of mind that creates difficulties later, during their working lives. It’s a form of `̀ culture trap’’. As such, the roles that women have been taught to play and the attitudes that they have been encouraged to assume seem to signal a certain `̀ second class’’. This is even more important in a group setting since group members will elect a leader who seems capable of representing the best interests of the group. Attitude toward leadership is a significant predictor for group assessed leader emergence (Kolb, 1997). This is particularly significant if women are to establish themselves as leaders in today’s team-based organizations where leadership is just as likely to be assumed as assigned. Findings suggest that the specific component of attitude toward leadership, more than the overall gender classification of masculinity, might be what causes group members to view individuals as leaders, although masculinity is still relevant (Kolb, 1997). Also linked to attitude is the encouragement and support received as part of an organization’s formal and informal system of feedback: `̀ By and large, blocked mobility breeds pessimism and disengagement among workers, regardless of their sex, whereas indications of opportunity foster engagement and optimism’’ (Cassirer and Reskin, 2000). Self-confidence There are further and more worrisome indications that women have internalized the noted second class attitude, resulting in a diminished self-confidence and, again, a disconnect with others’ expectations of leadership. `̀ The addition of self-confidence to the regression model for leadership emergence substantially improved its predictive ability’’ (Kolb, 1999). Jackson’s deprivation theory merits mention in the context of self-confidence as well. `̀ Relative deprivation theory has been used to explain women’s apparent satisfaction with less . . . for example women achieving the same hierarchical levels as did men despite lower incomes’’ (Kirchmeyer, 1998; Jackson, 1989). Accepting less may also signal a lack of self-confidence and may also ensure that women effectively get less in the [ 46 ] Steven H. Appelbaum, Lynda Audet and Joanne C. Miller Gender and leadership? Leadership and gender? A journey through the landscape of theories Leadership & Organization Development Journal 24/1 [2003] 43-51 way of money, rewards and praise for their leadership skills. Experience Although both experience and masculinity are significantly correlated with groupassessed leader emergence, neither emerges as a significant predictor (Kolb, 1997). Further research (Kolb, 1999) suggests that `̀ measures of attitude, experience and selfconfidence should continue to be examined for their predictive value in leader emergence. These scales appear to be more predictive than masculinity of leader emergence and have the advantage of not relying on gender stereotype.’’ This may indicate that women need to be in the pipeline long enough to gain the required experience. Otherwise, they risk being perceived as lacking the credibility to possess leadership potential. The corporate environment Indirectly linked to issues of attitude and selfconfidence is the corporate environment in which women work. It is often in this demanding and challenging environment that women are expected to excel and are evaluated accordingly. Women experience work environments in which they feel less welcome, and somewhat threatened by what they perceive as selfserving domineering cultures. Organizations typically favor stereotypical masculine values and reward practices that conform to sex-based values. As such, the more masculine attributes of being domineering, tough-minded and powerful may be noticed by more women to the extent they are taught or socialized to display different values in their behavior (Wicks and Bradshaw, 1999). Further, the status quo is unlikely to change in the short or even mid-term since `̀ organizations are structured to protect male power and reward masculinity accordingly, for example, rewarding analytical rationality above intuition, and task-orientation over people orientation’’ (Rigg and Sparrow, 1994). Furthermore, `̀ gender-based stereotyping and the closed circle of the `old boy network’ are strong social forces that are slow to change’’ (Oakley, 2000). As can be expected in any situation, there is safety in numbers: according to psychologists, women are at highest risk of stereotypic appraisal when they form less than 15 to 25 percent of a management level. When women move in large numbers into uppermanagement, as they are now poised to do in many professions, the evaluative norms will change. In theory at least, women will then be seen not as women managers, but simply as managers (Jamieson, 1995). This is perhaps in line with a growing body of evidence that suggests that entrepreneurship is on the rise much more for women than for men since women may be driven to it. Women entrepreneurs, regardless of whether they are intentional entrepreneurs or corporate climbers, have found that the corporate atmosphere stifled their aspirations to pursue new challenges (Moore and Buttner, 1997). With regard to gender, Jacobs (1989) argues that opportunities for employment in male dominated occupations have increased, but men’s resistance to women’s presence has resulted in nearly as many women leaving these jobs (Maume, 1999). Organizations foster or discourage their employees’ aspirations for promotion. By disproportionately employing women in jobs that lack regular promotion procedures or less frequently implementing regular promotion procedures in women’s jobs, employers not only reduce women’s chances for promotion, they in effect encourage some women to give up hope of being promoted (Cassirer and Reskin, 2000). Organizations that ignore their highachieving women by not offering them opportunities for promotion risk having them go elsewhere and therefore risk the loss of the value of the human capital they employ. The old boys’ network Despite high levels of political correctness popular in North American corporate society today, the `̀ old boys’ network’’ is alive and well and not always women’s greatest source of support. In fact, there is active resistance by men. They generate institutional impediments to stall woman’s advance in organizations. At a cultural level, they foster solidarity between men and sexualize, threaten, marginalize, control and divide women (Rigg and Sparrow, 1994). Contributing to the old boys’ ability to do this is the general fact that men still tend to have the power. For example, male managers, who often make decisions affecting the upward mobility of women, have been found to perceive the characteristics needed for managerial success as being associated with those generally attributed to men. The fact that male managers may not consider female characteristics important for managerial success can negatively impact decisions made by males concerning women’s careers, including job placement, promotion and access to development and training opportunities (Burke and Collins, 2001). It is clear from this discussion of selected causal factors how diverse and complex a [ 47 ] Steven H. Appelbaum, Lynda Audet and Joanne C. Miller Gender and leadership? Leadership and gender? A journey through the landscape of theories Leadership & Organization Development Journal 24/1 [2003] 43-51 topic leadership can become. It goes far beyond the qualities of the leader and those individuals directly interacting with that leader. To even begin to fairly evaluate a leader’s abilities necessitates evaluating the entirety of the leader’s environment. As long as others tend to attribute women’s accomplishments to unstable, external factors, to make inaccurate predictions about women’s commitments, to believe that women lack the suitable traits for management, and to allow cross-sexuality to impair relationships at work, women’s success determinants will probably differ from men’s (Kirchmeyer, 1998). Attitudinal drivers According to Claes (1999), new values, sometimes called feminine values, have appeared in business. These values contrast with the competitive and authoritative approach usually associated with traditional masculine management as they are based on consensual relations and inspire a different management approach to communications, leadership, negotiations, organization and control. Increasingly, this rebalancing of values is seen as a key to business success. Research aggregated from numerous sources acknowledges differences in a male versus female approach to leadership. A variety of descriptors attributed to males and females, reads as follows: Male Female Structure Consideration Transactional Transformational Autocratic Participative Instruction-giving Socio-expressive Business-oriented People-oriented Much contemporary thinking, however, conceptualizes a feminine style of leadership that is singularly different from its male counterpart. Some theorists (Helgesen, 1990), suggest that certain feminine characteristics give the woman leader an advantage. Characteristics described as essentially feminine are, among others, heightened communication skills (especially the ability to be a good listener and to be empathetic); advanced intermediary skills (for negotiation and conflict resolution); well-developed interpersonal skills and a soft approach to handling people (Stanford et al., 1995). Further, a variety of work now concurs with the essence of this direction: `̀ feminine characteristics’’ are more appropriate for `̀ transformational’’ leadership and `̀ masculine characteristics’’ more appropriate for transactional leadership (Hare et al., 1997). Kabacoff (1998) finds that women tend to be more highly rated on empathy (demonstrating an active concern for people and their needs, forming close, supportive relationships with others), and communication (stating clear expectations for others, clearly expressing thoughts and ideas, maintaining flow of communications) than men. Women are also more highly rated on people skills (sensitivity to others, likeableness, ability to listen and to develop effective relationships with peers and with those to whom they report). However, they are not seen as more outgoing (acting in an extroverted, friendly, informal fashion) or more co-operative in their leadership styles. Contrary to expectations, women tend to score higher on a leadership scale measuring an orientation towards production (strong pursuit of achievement, holding high expectations for self and others) and the attainment of results. Men tend to score higher on scales assessing an orientation towards strategic planning and organizational vision. Women tend to be higher on people-oriented leadership skills, men on business-oriented leadership skills. Overall, bosses see men and women as equally effective, while peer and direct assessment rate women as slightly higher than men (Claes, 1999; Kabacoff, 1998). These findings are truly encouraging on three levels. The first level is the idea that women can build a more inclusive, rewarding organization where employees on every level can aspire to be the best that they can be. The findings indicate that women employ a transformational leadership style. The analogy of a wheel with a hub depicts the organizational structure of a leader positioned at the center, with the subordinates connected to her and to each other at the rim. This conveys a collaborative team approach that empowers both employees and clients. Women entrepreneurs often integrate multiple organizational roles andmultiple dimensions of their lives, such as balancing home and work, into a leadership role (Moore and Buttner, 1997). The second level at which this work seems promising is that it may help banish wellmeant but somewhat detrimental thinking: `̀ As long as women are believed to fit the requirements of management poorly, female managers should be cautious about demonstrating a feminine orientation that could reinforce perceptions of incompetence in the minds of organizational decision makers’’ (Kirchmeyer, 1998). According to Kirchmeyer (1998) the differential effects of the individual [ 48 ] Steven H. Appelbaum, Lynda Audet and Joanne C. Miller Gender and leadership? Leadership and gender? A journey through the landscape of theories Leadership & Organization Development Journal 24/1 [2003] 43-51 determinants were consistent with our expectations. Masculinity has a stronger positive effect on women’s perceptions of success than on men’s. Third, and most encouraging, is that this learning may finally steer research away from male versus female issues to effective versus ineffective issues: `̀ These findings support the conclusion that leadership style/ use of power is more of a choice based on an analysis of the situation than an inherent gender predisposition and that leadership style differences, if any, may blur as gendermixed management teams become more common in the workplace’’ (Langford et al., 1998). Summary and conclusions This review was prompted by the significant under-representation of women in today’s senior corporate ranks and the theory that a core issue may be skewed perceptions of leadership ability or, more specifically, women’s leadership inability. The three specific questions that were formulated at the outset were: 1 Are women’s leadership styles truly different from men’s? 2 Are these styles less likely to be effective? 3 Is the assessment that women leadership styles fact-based or a perception that has become a reality? The literature can be roughly grouped into four schools of thought. The first approach examined seems to be based on the premise that leadership is biologically determined and innate for men. A second area of thought acknowledges the role of socialization and explores the notion of gender role as a determinant of leadership. A third concept involves the identification and consideration of a variety of other contributing causal factors ± beyond gender role ± that could predict and influence, leadership effectiveness and emergence. The fourth perspective accepts that there may well be a difference in the way men and women approach leadership and attempts to understand and articulate this difference. To conclude, the original questions and those restated above can be answered as follows: Question one: Yes, women’s leadership style is, at this point, different from men’s but men can learn from and adopt `̀ women’s’’ style and use it effectively as well. In other words, effective leadership is not the exclusive domain of either gender and both can learn from the other. Question two: No, women’s styles are not at all likely to be less effective; in fact, they are more effective within the context of teambased, consensually-driven organizational structures that are more prevalent in today’s world. Question three: The assessment that a woman’s leadership style is less effective than a man’s is not fact-based but rather driven, by socialization, to a perception that certainly persists. The inescapable reality is that, within the senior ranks of corporate North America (and elsewhere), women remain conspicuous by their absence. The irony of the learning deserves mention. When women attempt to prove their competence by `̀ acting like men’’, they are considered to be less than women. When there seems to be some merit in what would normally have been considered a `̀ female’’ approach, men adopt it as their own. What was seen as weak is now thought of as flexible; what was emotional now combines with the rational to bring balance. The concept of `̀ greater good’’, once inappropriate in the competitive world of business, is now visionary. Surely, the qualities themselves have not changed. Have attitudes changed? This leads to consideration of the following questions for further research: What are some defensible rationales behind the under-representation of women in senior corporate ranks? If the reason why women are underrepresented in senior management is driven by negative perceptions of women’s abilities, how can this be corrected? Is there need for a new model for re-socialization? How can we expand on the learning from environmental factor work to better understand factors predicting and influencing leadership effectiveness? Should leadership effectiveness training for women follow a different model than for men if re-socialization merits consideration? Are other scales, such as Myers Briggs categories, better predictors of leadership effectiveness or leadership emergence? It can also be suggested that research focusing on the debate between male and female effectiveness should be redirected since it seems quite clear that questions regarding leader effectiveness and leader emergence are better linked to the individual rather than to an individual’s sex or even gender role.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

The Study of Creative Leadership Styles Chiefs Sport Committees in Ghom Province with Caution to Their Leadership styles (Transformational, Transactional and People Oriented)

The purpose of this study was to investigate Creative Leadership Styles Chiefs Sport Committees in Qom Province with Caution to their Leadership styles (Transformational, Transactional and People oriented). Between 35 sport committees, 33 assistant managers and committee managers sport committees (n=63) completed the two questionnaire of individual characteristics and Creative leadership questi...

متن کامل

Relationship between leadership styles of heads of education departments and faculties’ job satisfaction

Abstract Introduction: Leadership is one of the important responsibilities of leaders, science and art of influencing others is to access goals. Leadership style or management determines atmosphere, culture and rules which control organization. Heads of departments can increase job satisfaction, employees' organizational obligation and efficiency by using leadership styles. Objective: This stud...

متن کامل

Gender Diversity in Management Positions and Organizational Performance: A Review of Literature

In this term paper, diversity in management positions and organizational performance is analyzed using gender diversity as a mediating role. The analysis is done based on the review of related literature. An organization’s success and competitiveness depends upon its ability to embrace diversity and realize the benefits. The success and failure of an organization is also linked with its leaders...

متن کامل

Authentic leadership: application to women leaders

The purpose of this perspective article is to present the argument that authentic leadership is a gendered representation of leadership. We first provide a brief history of leadership theories and definitions of authentic leadership. We then critique authentic leadership and offer arguments to support the premise that authentic leadership is not gender-neutral and is especially challenging for ...

متن کامل

Who is an Ideal Organizational Leader in Iran? Examining the Content, Structure, and Consequences of Iranian Implicit Leadership Theories (IILTS)

Implicit Leadership Theories (ILTs) are individuals’ perceptions of the traits and behaviors characterizing leaders. Four studies investigated the reliabilities and different types of validities for a scale developed to measure Iranian Implicit leadership Theories (IILTs). Study 1 used a qualitative method to extract the implicit theories of ideal leadership after interviewing 27 experts. The I...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2003