"The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought", Emily M. Levesque, Philip Massey, K. A. G. Olsen, Bertrand Plez, Eric Josselin, Andre Maeder, and Georges Meynet, The Astrophysical Journal628, #2 (August 2005), pp. 973-985, doi:10.1086/430901, Bibcode:2005ApJ...628..973L.
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"The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought", Emily M. Levesque, Philip Massey, K. A. G. Olsen, Bertrand Plez, Eric Josselin, Andre Maeder, and Georges Meynet, The Astrophysical Journal628, #2 (August 2005), pp. 973-985, doi:10.1086/430901, Bibcode:2005ApJ...628..973L.