https://9lib.org/document/zkw6jw04-verticesisdenotedby-thecardinalitiesofthesesetsaredenotedby-wedenotethevertexsetofagraph-thegraphsconsideredinthispaperarefinite-undirectedandhavenoloopsormultipleedges-mostofthenotationsthatfollowcanbefoundin-edgedisjointfreegraphs-discussionesmathematica.html