Superconductivity of Rb3C60: breakdown of the Migdal-Eliashberg theoryE. Cappelluti, C. Grimaldi, L. Pietronero, S. Strässler and G. A. UmmarinoEur. Phys. J. B, 21 3 (2001) 383-391DOI: https://doi.org/10.1007/PL00011123