SROYSANG, B. On the $n$-th Derivative of the Exponential Integral Functions. Communications in Mathematics and Applications, [S. l.], v. 4, n. 2, p. 141–144, 2013. DOI: 10.26713/cma.v4i2.170. Disponível em: https://www.journals.rgnpublications.com/index.php/cma/article/view/170. Acesso em: 18 aug. 2025.