Head-on and head-off collisions of discrete breathers in two-dimensional anharmonic crystal latticesAndrei A. Kistanov, Sergey V. Dmitriev, Alexander P. Chetverikov and Manuel G. VelardeEur. Phys. J. B, 87 9 (2014) 211DOI: https://doi.org/10.1140/epjb/e2014-50343-6