Residual symmetry analysis and CRE integrability of the (3 + 1) -dimensional Burgers systemXi-Zhong Liu, Jun Yu, Zhi-Mei Lou and Xian-Min QianEur. Phys. J. Plus, 133 12 (2018) 503DOI: https://doi.org/10.1140/epjp/i2018-12301-x