Article history: Received 15 June 2014 Received in revised form 8 July 2014 Accepted 4 September 2014 Available online 20 September 2014

Article history: Received 15 April 2014 Received in revised form 29 September 2014 Accepted 28 October 2014 Available online 4 November 2014

Article history: Received 19 February 2014 Received in revised form 28 October 2014 Accepted 28 October 2014 Available online 4 November 2014

Article history: Received 19 March 2014 Received in revised form 14 October 2014 Accepted 4 November 2014 Available online 18 November 2014

Article history: Received 14 February 2014 Received in revised form 4 June 2014 Accepted 12 June 2014 Available online 19 June 2014

Article history: Received 14 June 2014 Received in revised form 30 September 2014 Accepted 4 November 2014 Available online 11 November 2014

Article history: Received 26 February 2014 Received in final revised form 30 April 2014 Available online 4 June 2014

Article history: Received 22 March 2014 Received in revised form 4 August 2014 Accepted 13 August 2014 Available online 23 August 2014

Article history: Received 27 May 2014 Received in revised form 4 August 2014 Accepted 25 August 2014 Available online 27 September 2014

Article history: Received 4 May 2014 Received in revised form 9 December 2014 Accepted 12 December 2014 Available online 26 December 2014