12th Cologne-Twente workshop on graphs and combinatorial optimization (CTW 2013)

Weare pleased to present this special issue ofDiscrete AppliedMathematics, which is devoted to the 12th Cologne-Twente Workshop on Graphs and Combinatorial Optimization (CTW 2013), held at the University of Twente, Enschede, The Netherlands, between May 21 and May 23, 2013. More than 80 scientists from all over the world attended the workshop, and we take this opportunity to thank all CTW 2013 participants for their presentations and lively discussions at the workshop. After the workshop, we invited the participants and the community at large to submit manuscripts with research results related to the themes and topics of the workshop. From the submitted manuscripts, we have selected, after a careful refereeing process, twelve articles to be included in this special issue. We thank the reviewers for their insightful reports and the authors for the quality of their contributions. Special thanks are due to Endre Boros, Editor-in-Chief, who accepted to host this issue dedicated to CTW 2013 in Discrete Applied Mathematics, thereby following a long tradition. We also thank Katie D’Agosta, Publications Manager, for her help and valuable support. The CTW started as a series of biennial meetings at the Universities of Cologne in Germany and Twente in the Netherlands. Ever-increasing interest has turned the CTW into a now annual event with several other universities as additional partners. The scope of the workshop comprises the theory and applications of discrete algorithms, graphs, and combinatorial structures in a broad sense. We hope for a continuing interest in these CTW workshops and are looking forward to contributions in the future from all interested researchers.