Helmi, A; van Leeuwen, F; McMillan, P J; Massari, D; Antoja, T; Robin, A; Lindegren, L; Bastian, U (2018). "Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way". Astronomy and Astrophysics. 616. Gaia Collaboration: A12. arXiv:1804.09381. Bibcode:2018A&A...616A..12G. doi:10.1051/0004-6361/201832698. S2CID260496632.
Helmi, A; van Leeuwen, F; McMillan, P J; Massari, D; Antoja, T; Robin, A; Lindegren, L; Bastian, U (2018). "Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way". Astronomy and Astrophysics. 616. Gaia Collaboration: A12. arXiv:1804.09381. Bibcode:2018A&A...616A..12G. doi:10.1051/0004-6361/201832698. S2CID260496632.
Stobie, R. S. (1971). "On the Difference Between the Oosterhoff Types i and II Globular Clusters". The Astrophysical Journal. 168: 381. Bibcode:1971ApJ...168..381S. doi:10.1086/151094.
harvard.edu
ui.adsabs.harvard.edu
Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849 (849): 11–14. Bibcode:1927BHarO.849...11S.
Helmi, A; van Leeuwen, F; McMillan, P J; Massari, D; Antoja, T; Robin, A; Lindegren, L; Bastian, U (2018). "Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way". Astronomy and Astrophysics. 616. Gaia Collaboration: A12. arXiv:1804.09381. Bibcode:2018A&A...616A..12G. doi:10.1051/0004-6361/201832698. S2CID260496632.
Stobie, R. S. (1971). "On the Difference Between the Oosterhoff Types i and II Globular Clusters". The Astrophysical Journal. 168: 381. Bibcode:1971ApJ...168..381S. doi:10.1086/151094.
messier-objects.com
admin (2015-01-17). "Messier 2". Messier Objects. Retrieved 2023-04-29.
Helmi, A; van Leeuwen, F; McMillan, P J; Massari, D; Antoja, T; Robin, A; Lindegren, L; Bastian, U (2018). "Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way". Astronomy and Astrophysics. 616. Gaia Collaboration: A12. arXiv:1804.09381. Bibcode:2018A&A...616A..12G. doi:10.1051/0004-6361/201832698. S2CID260496632.