Karandjulov, L. (1999) “Asymptotic solution of definite class of singularly perturbed linear boundary-value problems for ordinary differential equations”, Ann. Sofia Univ. Fac. Math. and Inf, 91, pp. 79–95. Available at: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/271 (Accessed: 4 December 2024).