Private movements of rolling sphere on absolutely rough tore. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 86, n. 2, p. 123–132, 1994. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/509. Acesso em: 4 feb. 2026.