A new determination of the 4He and 3He masses in a Penning trap T. Fritioff, C. Carlberg, G. Douysset, R. Schuch and I. Bergström Eur. Phys. J. D, 15 2 (2001) 141-143 Published online: 15 August 2001 DOI: 10.1007/s100530170159