1. V. I. Gorbachev, ‘‘About one approach to a solution of linear differential equations with variable coefficients,’’ Lobachevskii J. Math. 40 (7), 969–980 (2019).
2. V. I. Gorbachev, ‘‘The homogenization method of Bakhvalov–Pobedrya in the composite mechanics,’’ Mosc. Univ. Mech. Bull. 71, 137–141 (2016).
3. V. I. Gorbachev, ‘‘Integral formulas of solutions of the basic linear differential equations of mathematical physics with variable factors,’’ Chebyshev. Sb. 18, 138–160 (2017).
4. E. Kamke, Differentialgleichungen Losungsmethoden Und Losungen (Akademische Verlagsgesellschaft, Leipzig, 1957).
5. V. V. Stepanov, Course of Differential Equations (Fizmatlit, Moscow, 1958) [in Russian].