Analytic study of solutions for a (3 + 1) -dimensional generalized KP equation Hui Gao, Wenguang Cheng, Tianzhou Xu and Gangwei Wang Eur. Phys. J. Plus, 133 3 (2018) 116 Published online: 20 March 2018 DOI: 10.1140/epjp/i2018-11945-8