Multi-reference many-body perturbation theory for nuclei - I. Novel PGCM-PT formalism M. Frosini, T. Duguet, J.-P. Ebran and V. Somà Eur. Phys. J. A, 58 4 (2022) 62 Published online: 08 April 2022 DOI: 10.1140/epja/s10050-022-00692-z