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Sota, A.; Maíz Apellániz, J.; Walborn, N. R.; Alfaro, E. J.; Barbá, R. H.; Morrell, N. I.; Gamen, R. C.; Arias, J. I. The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500. The Astrophysical Journal Supplement. Bibcode:2011ApJS..193...24S. arXiv:1101.4002. doi:10.1088/0067-0049/193/2/24.
UBV photometry of stars whose positions are accurately known. VII. Astronomy and Astrophysics Supplement Series: 591–592. Bibcode:1993A&AS..100..591O. ISSN 0365-0138.
Sota, A.; Maíz Apellániz, J.; Walborn, N. R.; Alfaro, E. J.; Barbá, R. H.; Morrell, N. I.; Gamen, R. C.; Arias, J. I. The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500. The Astrophysical Journal Supplement. Bibcode:2011ApJS..193...24S. arXiv:1101.4002. doi:10.1088/0067-0049/193/2/24.
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Kaltcheva, N.; Golev, V. Improved Distances to Several Galactic OB Associations. Stellar Clusters & Associations: A RIA Workshop on Gaia. 2011: 299–303. Bibcode:2011sca..conf..299K. arXiv:1107.3758.
UBV photometry of stars whose positions are accurately known. VII. Astronomy and Astrophysics Supplement Series: 591–592. Bibcode:1993A&AS..100..591O. ISSN 0365-0138.