“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, vol. 2, no. 1, Mar. 1999, pp. 19-29, https://twinhead.imath.kiev.ua/index.php/nosc/article/view/36.