Liouvillian integrability of the three-dimensional generalized Hénon–Heiles Hamiltonian Idriss El Fakkousy, Jaouad Kharbach, Walid Chatar, Mohamed Benkhali, Abdellah Rezzouk and Mohammed Ouazzani-Jamil Eur. Phys. J. Plus, 135 7 (2020) 612 Published online: 29 July 2020 DOI: 10.1140/epjp/s13360-020-00625-z