Evtukhov , V. M., and A. G. Chernikova. “On the Asymptotic of Solutions of the Second-Order Differential Equations With Rapidly Varying Nonlinearities”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 73, no. 4, Apr. 2021, pp. 488 -05, doi:10.37863/umzh.v73i4.627.