Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance?U. Hincelin, V. Wakelam, F. Hersant, S. Guilloteau, J. C. Loison, P. Honvault and J. TroeA&A, 530 (2011) A61DOI: https://doi.org/10.1051/0004-6361/201016328