Flaška, V.; Ježek, J.; Kepka, T.; Kortelainen, J. Transitive Closures of Binary Relations I(PDF). Prague: School of Mathematics - Physics Charles University. 2007: 1 [2013-08-20]. (原始内容(PDF)存档于2013-11-02). Lemma 1.1 (iv). Note that this source refers to asymmetric relations as "strictly antisymmetric".
Flaška, V.; Ježek, J.; Kepka, T.; Kortelainen, J. Transitive Closures of Binary Relations I(PDF). Prague: School of Mathematics - Physics Charles University. 2007: 1 [2013-08-20]. (原始内容(PDF)存档于2013-11-02). Lemma 1.1 (iv). Note that this source refers to asymmetric relations as "strictly antisymmetric".