On the difference between proton and neutron spin-orbit splittings in nuclei V.I. Isakov, K.I. Erokhina, H. Mach, M. Sanchez-Vega and B. FogelbergEur. Phys. J. A, 14 1 (2002) 29-36DOI: https://doi.org/10.1140/epja/iepja1393