Viable inflationary models in a ghost-free Gauss–Bonnet theory of gravity Shin’ichi Nojiri, S. D. Odintsov, V. K. Oikonomou, N. Chatzarakis and Tanmoy Paul Eur. Phys. J. C, 79 7 (2019) 565 Published online: 04 July 2019 DOI: 10.1140/epjc/s10052-019-7080-1