Mid-IR observations of Galactic H II regions: Constraining ionizing spectra of massive stars and the nature of the observed excitation sequencesC. Morisset, D. Schaerer, J.-C. Bouret and F. MartinsA&A, 415 2 (2004) 577-594DOI: https://doi.org/10.1051/0004-6361:20034622
