ZASHEV, J. COMBINATORY SPACES VERSUS OPERATIVE SPACES WITH STORAGE OPERATION. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 100, p. 123–142, 2011. Disponível em: https://ftl5.uni-sofia.bg/index.php/fmi/article/view/250. Acesso em: 14 apr. 2025.