Sinaisky , E.S. (1988) “Approximation method in one boundary value problem for linear differential equation with polynomial coefficients”, Ukrains’kyi Matematychnyi Zhurnal, 40(2), pp. 248–253. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/9127 (Accessed: 17 February 2026).