Hydrogen and helium traces in type Ib-c supernovae A. Elmhamdi, I. J. Danziger, D. Branch, B. Leibundgut, E. Baron and R. P. Kirshner A&A, 450 1 (2006) 305-330 Published online: 03 April 2006 DOI: 10.1051/0004-6361:20054366