Phelps, Randy L.; Janes, Kenneth A. (1993). "Young open clusters as probes of the star-formation process. 2: Mass and luminosity functions of young open clusters". Astronomical Journal. Quyển 106 số 5. tr. 1870–1884. Bibcode:1993AJ....106.1870P. doi:10.1086/116772.
Humphreys, R. M. (1978). "Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way". Astrophysical Journal Supplement Series. Quyển 38. tr. 309–350. Bibcode:1978ApJS...38..309H. doi:10.1086/190559.
Phelps, Randy L.; Janes, Kenneth A. (1993). "Young open clusters as probes of the star-formation process. 2: Mass and luminosity functions of young open clusters". Astronomical Journal. Quyển 106 số 5. tr. 1870–1884. Bibcode:1993AJ....106.1870P. doi:10.1086/116772.
Humphreys, R. M. (1978). "Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way". Astrophysical Journal Supplement Series. Quyển 38. tr. 309–350. Bibcode:1978ApJS...38..309H. doi:10.1086/190559.