L. P. Bassino, S. Waldhausen, & R. E. Martinez (2000). «CCD photometry in the region of NGC 6994: The remains of an old open cluster». Astronomy & Astrophysics. 355: 138–144. Bibcode:2000A&A...355..138B !CS1 manut: Nomes múltiplos: lista de autores (link)