Samоіlenkо A. M. “The Numerical-Analytical Method of Investigating Periodic Systems of Ordinary Differential Equations. II”. Ukrains’kyi Matematychnyi Zhurnal 18, no. 2 (March 5, 1966): 50–59. Accessed April 27, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8716.