Threshold dynamics of difference equations for SEIR model with nonlinear incidence function and infinite delaySoufiane Bentout, Salih Djilali, Sunil Kumar and Tarik Mohammed TouaoulaEur. Phys. J. Plus, 136 5 (2021) 587DOI: https://doi.org/10.1140/epjp/s13360-021-01466-0