Mason, Brian D.; Hartkopf, William I.; Gies, Douglas R.; Henry, Todd J.; Helsel, John W. (2009). «The High Angular Resolution Multiplicity of Massive Stars». The Astronomical Journal137 (2): 3358. doi:10.1088/0004-6256/137/2/3358. Bibcode: 2009AJ....137.3358M.
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Anand, M. Y.; Kagali, B. A.; Murthy, Jayant (2009). «Study of Bubble nebula using IUE high resolution spectra». Bulletin of the Astronomical Society of India37 (1): 1. Bibcode: 2009BASI...37....1A.
Mason, Brian D.; Hartkopf, William I.; Gies, Douglas R.; Henry, Todd J.; Helsel, John W. (2009). «The High Angular Resolution Multiplicity of Massive Stars». The Astronomical Journal137 (2): 3358. doi:10.1088/0004-6256/137/2/3358. Bibcode: 2009AJ....137.3358M.