LuchkaA. Y., and MamatovT. D. 1994. “Solution of Volterra Integral Equations of the Second Kind With Small Nonlinearities by a Spline-Iteration Method”. Ukrains’kyi Matematychnyi Zhurnal 46 (4), 433–437. https://umj.imath.kiev.ua/index.php/umj/article/view/5742.