K. Boyadzhiev, Victor H. Moll. The integrals in Gradshteyn and Ryzhik Part 26: The exponential integral. Sci. Ser. A Math. Sci. (N.S.) [Internet]. 2015 Jan. 30 [cited 2025 Jun. 28];26:19-30. Available from: https://revistas.usm.cl/scientia/article/view/225