Samoilenko, V. G., and Yu. I. Samoilenko. 2018. “Asymptotic $Σ$-Solutions to Singularly Perturbed Benjamin – Bona – Mahony Equation With Variable Coefficients”. Ukrains’kyi Matematychnyi Zhurnal 70 (2): 236-54. https://umj.imath.kiev.ua/index.php/umj/article/view/1554.