Er’omenkoV. O., and AliluikoA. M. “Quasiperiodic Solutions of Degenerate Linear Systems of Second-Order Ordinary Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 6 (June 25, 2010): 773–783. Accessed December 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2908.