Lu, Junfeng. “Analytical Approach to Kawahara Equation Using Variational Iteration Method and Homotopy Perturbation Method”. Topological Methods in Nonlinear Analysis 31, no. 2 (June 1, 2008): 287–293. Accessed July 22, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2008.020.