Hogg, Helen Battles Sawyer (October 1965). “Harlow Shapley and Globular Clusters”. Publications of the Astronomical Society of the Pacific77 (458): 336–46. Bibcode: 1965PASP...77..336S. doi:10.1086/128229.
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Hogg, Helen Battles Sawyer (October 1965). “Harlow Shapley and Globular Clusters”. Publications of the Astronomical Society of the Pacific77 (458): 336–46. Bibcode: 1965PASP...77..336S. doi:10.1086/128229.