Physical constraints derived from FCNC in the 3-3-1-1 model Duy Nguyen Tuan, Takeo Inami and Huong Do Thi Eur. Phys. J. C, 81 9 (2021) 813 Published online: 14 September 2021 DOI: 10.1140/epjc/s10052-021-09583-x