Azarbaijan Shahid Madani UniversityCommunications in Combinatorics and Optimization2538-21285120200601The topological ordering of covering nodes55601395810.22049/cco.2019.26119.1077ENGholam HassanShirdelUniversity of Qom0000000327594606NasrinKahkeshaniUniversity of QomJournal Article20180109The topological ordering algorithm sorts nodes of a directed graph such that the order of the tail of each arc is lower than the order of its head. In this paper, we introduce the notion of covering between nodes of a directed graph. Then, we apply the topological ordering algorithm on graphs containing the covering nodes. We show that there exists a cut set with forward arcs in these graphs and the order of the covering nodes is successive.http://comb-opt.azaruniv.ac.ir/article_13958_bb278a35f5e754d8fa7152e537a20961.pdf