BobochkoV. N. “On the Structure of Solutions of a System of Singularly Perturbed Differential Equations With Nondiagonalizable Limit Operator”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 50, no. 7, July 1998, pp. 867–876, https://umj.imath.kiev.ua/index.php/umj/article/view/4867.