MULTITIME ACTION RECURRENCES ON A MONOID. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 103, p. 53–60, 2016. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/53. Acesso em: 15 dec. 2025.