Baumgardt, H.; Hilker, M.; Sollima, A.; Bellini, A. (2019), "Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data", Monthly Notices of the Royal Astronomical Society, 482 (4): 5138–5155, arXiv:1811.01507, Bibcode:2019MNRAS.482.5138B, doi:10.1093/mnras/sty2997.
Cohen, Roger E.; et al. (December 2021), "Relative Ages of Nine Inner Milky Way Globular Clusters from Proper-motion-cleaned Color-Magnitude Diagrams", The Astronomical Journal, 162 (6), id. 228, arXiv:2109.08708, Bibcode:2021AJ....162..228C, doi:10.3847/1538-3881/ac281f.
Baumgardt, H.; Hilker, M.; Sollima, A.; Bellini, A. (2019), "Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data", Monthly Notices of the Royal Astronomical Society, 482 (4): 5138–5155, arXiv:1811.01507, Bibcode:2019MNRAS.482.5138B, doi:10.1093/mnras/sty2997.
Cohen, Roger E.; et al. (December 2021), "Relative Ages of Nine Inner Milky Way Globular Clusters from Proper-motion-cleaned Color-Magnitude Diagrams", The Astronomical Journal, 162 (6), id. 228, arXiv:2109.08708, Bibcode:2021AJ....162..228C, doi:10.3847/1538-3881/ac281f.
Baumgardt, H.; Hilker, M.; Sollima, A.; Bellini, A. (2019), "Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data", Monthly Notices of the Royal Astronomical Society, 482 (4): 5138–5155, arXiv:1811.01507, Bibcode:2019MNRAS.482.5138B, doi:10.1093/mnras/sty2997.
Cohen, Roger E.; et al. (December 2021), "Relative Ages of Nine Inner Milky Way Globular Clusters from Proper-motion-cleaned Color-Magnitude Diagrams", The Astronomical Journal, 162 (6), id. 228, arXiv:2109.08708, Bibcode:2021AJ....162..228C, doi:10.3847/1538-3881/ac281f.