This special issue gathers a selection of papers presented at GO IX, but was also open to contributions in the fields of research of the plenary speakers. All papers passed a careful refereeing process, which resulted in 19 papers, which can be roughly classified as 9 papers in graph theory, 5 in scheduling, and 5 in optimization. Several papers report results at the interplay of at least two of these three areas. The papers in the special issue report on investigations in a variety of topics. Link to the article
ARCHETTI, C., BERTAZZI, L., MILANIČ, M., SCHINDL, D. and VARONE, S. (2018). Preface: Special Issue on the Ninth International Colloquium on Graphs and Optimization (GO IX), 2014. Discrete Applied Mathematics, 234, pp. 1-2.