Zh.A. Sartabanov, B.Zh. Omarova, и A.Kerimbekov. «RESEARCH OF MULTIPERIODIC SOLUTIONS OF PERTURBED LINEAR AUTONOMOUS SYSTEMS WITH DIFFERENTIATION OPERATOR ON THE VECTOR FIELD». Известия НАН РК. Серия физико-математическая, вып. 6, декабрь 2019 г., сс. 63-79, https://journals.nauka-nanrk.kz/physics-mathematics/article/view/1694.