Traversable Morris–Thorne–Buchdahl wormholes in quadratic gravity Hoang Ky Nguyen and Mustapha Azreg-Aïnou Eur. Phys. J. C, 83 7 (2023) 626 Published online: 17 July 2023 DOI: 10.1140/epjc/s10052-023-11805-3