“A Construction of Asymptotic Solutions of Partial Systems of Differential Equations With a Deviation of the Argument and a Degenerate Matrix at the Derivatives”. Neliniini Kolyvannya 5, no. 4 (December 29, 2002): 527–539. Accessed January 22, 2026. https://twinhead.imath.kiev.ua/index.php/nosc/article/view/239.