NGC 6618

Number of stars per data source

	Reference  125 :    7 stars
	Reference  206 :    1 star
	Reference  591 :    1 star
	Reference  877 :    8 stars
	Reference  999 :    4 stars

125: Hanson M.M., Howarth I.D., Conti P.S.; (1997) Astrophys. J. 489, 698; The young massive stellar objects of M17; 1997ApJ...489..698H
206: Hiltner W.A.; (1956) Astrophys. J. Suppl. 2, 389; Photometric, polarization and spectrographic observations of O and B stars; 1956ApJS....2..389H
591: Garmany C.D., Vacca W.D.; (1991) Publ. Astron. Soc. Pacific 103, 347; New spectral classifications for O-type stars in the northern hemisphere; 1991PASP..103..347G
999: Houk N., Cowley A.P., Smith-Moore M.; University of Michigan (Ann Arbor) Vol 1 (1975), Vol 2 (1978), Vol 3 (1982), Vol 4 (1988), Vol 5 (1999); The University of Michigan Catalogue of two-dimensional Spectral Types for the HD stars; 1975mctd.book.....H