ZAPRYANOV, Z.; MARKOV, N. On some applications of the singularity method. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 88, p. 5–20, 1996. Disponível em: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/372. Acesso em: 24 nov. 2024.