Searching for O2 in the SMC: - Constraints on oxygen chemistry at low metallicities C. D. Wilson, A. O. H. Olofsson, L. Pagani, R. S. Booth, U. Frisk, Å. Hjalmarson, M. Olberg and Aa. Sandqvist A&A, 433 1 (2005) L5-L8 Published online: 14 March 2005 DOI: 10.1051/0004-6361:200500024