Scale invariance vs. conformal invariance: holographic two-point functions in Horndeski gravity Yue-Zhou Li, H. Lü and Hao-Yu Zhang Eur. Phys. J. C, 79 7 (2019) 592 Published online: 12 July 2019 DOI: 10.1140/epjc/s10052-019-7096-6