A coincidence theorem for orthogonal maps. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 86, n. 1, p. 95–106, 1994. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/443. Acesso em: 17 dec. 2025.