On the effective enumerations of partial structures. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 83, n. 1, p. 29–37, 1992. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/482. Acesso em: 12 jan. 2026.