SiO excitation from dense shocks in the earliest stages of massive star formation S. Leurini, C. Codella, A. López-Sepulcre, A. Gusdorf, T. Csengeri and S. Anderl A&A, 570 (2014) A49 Published online: 15 October 2014 DOI: 10.1051/0004-6361/201424251