Nonlaopon, K., T. Nuntigrangjana, and S. Putjuso. “Distributional solutions of nth-order differential equations of the Bessel equation”. RMUTSB ACADEMIC JOURNAL, vol. 5, no. 1, Jan. 2017, pp. 1-10, https://li01.tci-thaijo.org/index.php/rmutsb-sci/article/view/99828.