传递约简和传递闭包都是有向无环图的特有概念<!-- is uniquely defined 唯一的? -->。相反的,对于有向有环图,可以存在多个与原图有着相同可达性的最简子图。<ref>{{citation|title=Digraphs: Theory, Algorithms and Applications|series=Springer Monographs in Mathematics|first1=Jørgen|last1=Bang-Jensen|first2=Gregory Z.|last2=Gutin|publisher=Springer|year=2008|isbn=978-1-84800-998-1|url=https://books.google.com/books?id=4UY-ucucWucC&pg=PA36|contribution=2.3 Transitive Digraphs, Transitive Closures and Reductions|pages=36–39}}.</ref> | 传递约简和传递闭包都是有向无环图的特有概念<!-- is uniquely defined 唯一的? -->。相反的,对于有向有环图,可以存在多个与原图有着相同可达性的最简子图。<ref>{{citation|title=Digraphs: Theory, Algorithms and Applications|series=Springer Monographs in Mathematics|first1=Jørgen|last1=Bang-Jensen|first2=Gregory Z.|last2=Gutin|publisher=Springer|year=2008|isbn=978-1-84800-998-1|url=https://books.google.com/books?id=4UY-ucucWucC&pg=PA36|contribution=2.3 Transitive Digraphs, Transitive Closures and Reductions|pages=36–39}}.</ref> |