restricting the graph constraints to special sets of digraphs. We discuss directed co-graphs, minimal series-parallel digraphs …

{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {NP}$$\end{document}-hard on acyclic digraphs by …}$$\end{document}-hard on series-parallel digraphs by providing a reduction from Partition. If in addition the number of scenarios is constant …-parallel digraphs for which we can solve the RobMCF≡\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage …

. We show that both problems are NP-hard even on oriented co-graphs and minimal series-parallel digraphs. Further, we …-parallel digraphs. …