Resonance instability of primordial gravitational waves during inflation in Chern–Simons gravityChengjie Fu, Jing Liu, Tao Zhu, Hongwei Yu and Puxun WuEur. Phys. J. C, 81 3 (2021) 204DOI: https://doi.org/10.1140/epjc/s10052-021-09001-2