MANUKIAN, S. N. . On Transitive Closures of Two-dimensional Strongly Positive Arithmetical Sets. Mathematical Problems of Computer Science, [S. l.], v. 45, p. 67–76, 2021. Disponível em: http://mpcs.sci.am/index.php/mpcs/article/view/169. Acesso em: 18 may. 2024.