In mathematics, Ky Fan's lemma (KFL) is a combinatorial lemma about labellings of triangulations. It is a generalization of Tucker's lemma. It was proved by Ky Fan in 1952.[1]
^"A Generalization of Tucker's Combinatorial Lemma with Topological Applications". The Annals of Mathematics. 56: 431. doi:10.2307/1969651.