SOSKOV, I. DEGREE SPECTRA AND CO-SPECTRA OF STRUCTURES. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 96, p. 45–68, 2004. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/160. Acesso em: 9 apr. 2025.