A simple proof of a coincidence theorem of Rubinstein-Walsh and generalizations. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 89, p. 113–116, 1997. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/360. Acesso em: 17 dec. 2025.