On edge irregular reflexive labeling for Cartesian product of two graphs Yongsheng Ke, Muhammad Javed Azhar Khan, Muhammad Ibrahim and Muhammad Kamran Siddiqui Eur. Phys. J. Plus, 136 1 (2021) 6 Published online: 01 January 2021 DOI: 10.1140/epjp/s13360-020-00960-1