Additional symmetry for the electronic shell in its ground state and many-electron effects P. Bogdanovich, A. Kyniene, R. Karazija, R. Karpuskiene and G. Gaigalas Eur. Phys. J. D, 11 2 (2000) 175-183 Published online: 15 August 2000 DOI: 10.1007/s100530070081