Extreme values of elastic strain and energy in sine-Gordon multi-kink collisions Aliakbar Moradi Marjaneh, Alidad Askari, Danial Saadatmand and Sergey V. Dmitriev Eur. Phys. J. B, 91 1 (2018) 22 Published online: 25 January 2018 DOI: 10.1140/epjb/e2017-80406-y