BOEV, T. A logarithmic class of semilinear wave equations. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 93, p. 93–108, 2001. Disponível em: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/206. Acesso em: 4 dec. 2024.