Variational calculation of some S-states of Coulomb three-body systems F. Arias de Saavedra, E. Buendía, F. J. Gálvez and A. Sarsa Eur. Phys. J. D, 13 2 (2001) 201-206 Published online: 15 February 2001 DOI: 10.1007/s100530170267