Solodkii, S. G. “Optimization of Algorithms for the Approximate Solution of the Volterra Equations With Infinitely Differentiable Kernels”. Ukrains’kyi Matematychnyi Zhurnal, vol. 46, no. 11, Nov. 1994, pp. 1534–1545, https://umj.imath.kiev.ua/index.php/umj/article/view/5592.