LEŚNIAK, Zbigniew. On the system of the Abel equations on the plane. Annales Mathematicae Silesianae, [S. l.], v. 9, p. 105–122, 1995. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14211. Acesso em: 8 may. 2025.