Pancino, E.; et al, Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682), Astronomy and Astrophysics, February 2010, 511: A56, Bibcode:2010A&A...511A..56P, doi:10.1051/0004-6361/200912965
Pancino, E.; et al, Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682), Astronomy and Astrophysics, February 2010, 511: A56, Bibcode:2010A&A...511A..56P, doi:10.1051/0004-6361/200912965