“A Study of Solutions That Are Continuously Differentiable and Bounded on $\mathbb{R}^2$ for a System of Nonlinear Integral Partial Differential Functional Equations With Linearly Transformed Argumen”. Neliniini Kolyvannya, vol. 6, no. 4, Dec. 2003, pp. 448-55, https://twinhead.imath.kiev.ua/index.php/nosc/article/view/279.