NoharaB. T. (2009) “Nonexistence theorem except the out-of-phase and in-phase solutions in the coupled van der Pol equation system”, Ukrains’kyi Matematychnyi Zhurnal, 61(8), pp. 1106-1129. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3084 (Accessed: 24November2024).