Paust, Nathaniel E. Q. m. fl.. (February 2010), «The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions», The Astronomical Journal139 (2): 476–491, Bibcode2010AJ....139..476P, DOI:10.1088/0004-6256/139/2/476.
Paust, Nathaniel E. Q. m. fl.. (February 2010), «The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions», The Astronomical Journal139 (2): 476–491, Bibcode2010AJ....139..476P, DOI:10.1088/0004-6256/139/2/476.
Shapley, Harlow; Sawyer, Helen B. (August 1927), «A Classification of Globular Clusters», Harvard College Observatory Bulletin (849): 11–14, Bibcode1927BHarO.849...11S.