STEFANOV, S. Ljusternik-Schnirelman category of the non-wandering set. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 84, p. 43–48, 1993. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/466. Acesso em: 25 nov. 2024.