“Determination of an exact solution to the integral Gelfand - Levitan - Marchenko equation for the Sturm - Liouville operators with the step-type potential” (2003) Neliniini Kolyvannya, 6(1), pp. 74–82. Available at: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/250 (Accessed: 22 January 2026).