First excitations of the spin 1/2 Heisenberg antiferromagnet on the kagomé lattice Ch. Waldtmann, H.-U. Everts, B. Bernu, C. Lhuillier, P. Sindzingre, P. Lecheminant and L. Pierre Eur. Phys. J. B, 2 4 (1998) 501-507 Published online: 15 April 1998 DOI: 10.1007/s100510050274