Upgren 1

Number of stars per data source

	Reference  345 :    6 stars
	Reference  737 :    5 stars
	Reference  741 :    7 stars
	Reference  868 :    7 stars

345: Castelaz M.W., Persinger T., Stein J.W., Prosser J., Powell H.D.; (1991) Astron. J. 102, 2103; Photometry of astrometric reference stars; 1991AJ....102.2103C
737: Upgren A.R., Rubin V.C.; (1965) Publ. Astron. Soc. Pacific 77, 355; An old open cluster near the north galactic pole; 1965PASP...77..355U
741: Upgren A.R., Philip A.G.D., Beavers W.I.; (1982) Publ. Astron. Soc. Pacific 94, 229; Upgren 1. An old open cluster near the end of its life; 1982PASP...94..229U
868: Ljunggren B.; (1965) Ark. Astron. 3, 535; A photoelectric and spectroscopic investigation of a region near the north galactic pole; 1965ArA.....3..535L