SROYSANG, B. Four Inequalities for the Exponential Integral Functions. Communications in Mathematics and Applications, [S. l.], v. 4, n. 2, p. 137–140, 2013. DOI: 10.26713/cma.v4i2.169. Disponível em: http://www.journals.rgnpublications.com/index.php/cma/article/view/169. Acesso em: 16 jun. 2025.