“…However, such problems are very difficult to solve either analytically or numerically, among all analytical methods [e.g. the variational iteration method (Naveed and He, 2019;He, 2020d), the Taylor series method He, 2019aHe, , 2020c, the exp-function method (He, 2013)], the homotopy perturbation method is the most effective tool for fractional differential equations (Nadeem et al, 2021;He and El-Dib, 2020a, 2020b, 2020cAnjum and He, 2020a;He, 1999;Anjum and He, 2020b;He and Jin, 2020;Yu et al, 2019;He et al, 2019).…”