“Periodic Solutions for a System of Linear Nonhomogeneous First Order Differen- Tial Equations With Rectangular Periodic Matrices”. Neliniini Kolyvannya 18, no. 1 (March 29, 2015): 38–54. Accessed April 12, 2026. https://nosc.imath.kiev.ua/index.php/nosc/article/view/768.