Homotopy perturbation method for modeling electrostatic structures in collisional plasmas Bothayna S. Kashkari and S. A. El-Tantawy Eur. Phys. J. Plus, 136 1 (2021) 121 Published online: 23 January 2021 DOI: 10.1140/epjp/s13360-021-01120-9