Vandenberg, D. A.; Brogaard, K.; Leaman, R.; Casagrande, L. (2013). "The Ages of 95 Globular Clusters as Determined Using an Improved Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues". The Astrophysical Journal775 (2): 134. doi:10.1088/0004-637X/775/2/134. Bibcode: 2013ApJ...775..134V.
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Vandenberg, D. A.; Brogaard, K.; Leaman, R.; Casagrande, L. (2013). "The Ages of 95 Globular Clusters as Determined Using an Improved Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues". The Astrophysical Journal775 (2): 134. doi:10.1088/0004-637X/775/2/134. Bibcode: 2013ApJ...775..134V.