BUSTAMANTE BARAHONA, P. Billings ovulation method and its contribution to familiar planification. Anales de Teología, [S. l.], v. 23, n. 2, p. 307–327, 2021. DOI: 10.21703/2735-6345.2021.23.02.006. Disponível em: https://revistas.ucsc.cl/index.php/analesdeteologia/article/view/1521. Acesso em: 23 apr. 2024.