Chuiko, S. M., E. V. Chujko, and A. V. Beluschenko. “Regularization of Periodic Boundary Value Problem With Impulse Action”. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics, no. 1061, May 2013, pp. 37-44, doi:10.26565/2221-5646-2013-1061-04.