Heavy-ion fusion reactions at extreme sub-barrier energies C. L. Jiang, B. B. Back, K. E. Rehm, K. Hagino, G. Montagnoli and A. M. Stefanini Eur. Phys. J. A, 57 7 (2021) 235 Published online: 15 July 2021 DOI: 10.1140/epja/s10050-021-00536-2