Geometry of gradient Einstein harmonic solitons in sequential warped products manifolds Akram Ali, Norah Alshehri, Fatemah Mofarreh and Yanlin Li Eur. Phys. J. Plus, 139 4 (2024) 339 Published online: 18 April 2024 DOI: 10.1140/epjp/s13360-024-05120-3