Baryogenesis and gravitational waves in the Zee–Babu model Vo Quoc Phong, Nguyen Chi Thao and Hoang Ngoc Long Eur. Phys. J. C, 82 11 (2022) 1005 Published online: 08 November 2022 DOI: 10.1140/epjc/s10052-022-10961-2