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