“The Asymptotic Solution of the Cauchy Problem for the Degenerate Singularly Perturbed Linear System in the Case of Multiple Spectrum of the Main Operator”. Neliniini Kolyvannya 2, no. 1 (March 29, 1999): 19–29. Accessed January 22, 2026. https://twinhead.imath.kiev.ua/index.php/nosc/article/view/36.