MURUGAPPAN, Mullai. Direct Product of SP-Algebra. Journal of Global Research in Mathematical Archives(JGRMA), [S. l.], v. 5, n. 5, p. 90–94, 2018. Disponível em: https://jgrma.com/index.php/jgrma/article/view/465. Acesso em: 28 apr. 2025.