Shawagfeh, N. T., y M. L. Glasser. 2011. «Uniform Asymptotic Solutions of Second Order Linear Differential Equations With Double Pole and Turning Point». Rev. Téc. Fac. Ing. Univ. Zulia 13 (1). https://mail.produccioncientificaluz.org/index.php/tecnica/article/view/5354.