Mitropolskiy, Y. A., D. T. Nguen, and D. A. Nguyen. “Random Oscillations in the Van Der Pol System under the Action of a Broadband Random Process”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 50, no. 11, Nov. 1998, pp. 1517–1521, https://umj.imath.kiev.ua/index.php/umj/article/view/4803.