Dirac and Majorana heavy neutrinos at LEP II F.M.L. Almeida Jr., Y.A. Coutinho, J.A. Martins Simões, M.A.B. do Vale and S. Wulck Eur. Phys. J. C, 22 2 (2001) 277-281 Published online: 12 November 2001 DOI: 10.1007/s100520100798