Jiang, Y.-Q., and J.-M. Zhu. “Solitary Wave Solutions for a Coupled MKdV System Using the Homotopy Perturbation Method”. Topological Methods in Nonlinear Analysis, vol. 31, no. 2, June 2008, pp. 359-67, https://apcz.umk.pl/TMNA/article/view/TMNA.2008.027.