NGC 6531

Number of stars per data source

	Reference  202 :    2 stars
	Reference  206 :    1 star
	Reference  207 :   12 stars

202: Morgan W.W., Code A.D., Whitford A.E.; (1955) Astrophys. J. Suppl. 2, 41; Studies in galactic structure. II. Luminosity classification for 1270 blue giant stars; 1955ApJS....2...41M
206: Hiltner W.A.; (1956) Astrophys. J. Suppl. 2, 389; Photometric, polarization and spectrographic observations of O and B stars; 1956ApJS....2..389H
207: Hoag A.A., Applequist L.; (1965) Astrophys. J. Suppl. 12, 215; Distance moduli of open clusters; 1965ApJS...12..215H