Neutron-proton mass difference in finite nuclei and the Nolen-Schiffer anomaly U. -G. Meißner, A. M. Rakhimov, A. Wirzba and U. T. Yakhshiev Eur. Phys. J. A, 36 1 (2008) 37-48 Published online: 29 April 2008 DOI: 10.1140/epja/i2008-10571-0