BISCHI, Gian-Italo; GARDINI, Laura; MIRA, Christian. New phenomena related to the presence of focal points in two-dimensional maps. Annales Mathematicae Silesianae, [S. l.], v. 13, p. 81–89, 1999. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14139. Acesso em: 7 may. 2025.