Massive pre-main-sequence stars in M17M. C. Ramírez-Tannus, L. Kaper, A. de Koter, F. Tramper, A. Bik, L. E. Ellerbroek, B. B. Ochsendorf, O. H. Ramírez-Agudelo and H. SanaA&A, 604 (2017) A78DOI: https://doi.org/10.1051/0004-6361/201629503