NGC 6997

Number of stars per data source

	Reference  369 : 1198 stars
	Reference  495 : 3252 stars

369: Villanova S., Baume G., Carraro G., Geminale A.; (2004) Astron. Astrophys. 419, 149; Optical photometry and spectral classification in the field of the open cluster NGC 6996 in the North America Nebula; 2004A&A...419..149V
495: Maciejewski G., Niedzielski A.; (2007) Astron. Astrophys. 467, 1065; CCD BV survey of 42 open clusters; 2007A&A...467.1065M