Chuiko, S. M., Chujko, E. V., & Beluschenko, A. V. (2013). Regularization of periodic boundary value problem with impulse action. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics, (1061), 37-44. https://doi.org/10.26565/2221-5646-2013-1061-04