Gamma-ray observations of the orion molecular clouds with the fermi large area telescope - Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R.; et al. (Institute of Physics Publishing, 2012)