Controllability for two-Kuznetsov-Ma solitons in a (2 + 1)-dimensional graded-index grating waveguideHai-Ping Zhu, Zhen-Huan Pan and Jian-Ping FangEur. Phys. J. D, 68 3 (2014) 69DOI: https://doi.org/10.1140/epjd/e2014-40681-x