Monaco, L.; Pancino, E.; Ferraro, F. R.; Bellazzini, M. (2004). Wide-field photometry of the Galactic globular cluster M22. Monthly Notices of the Royal Astronomical Society. 349 (4): 1278—1290. Bibcode:2004MNRAS.349.1278M. doi:10.1111/j.1365-2966.2004.07599.x.
Monaco, L.; Pancino, E.; Ferraro, F. R.; Bellazzini, M. (2004). Wide-field photometry of the Galactic globular cluster M22. Monthly Notices of the Royal Astronomical Society. 349 (4): 1278—1290. Bibcode:2004MNRAS.349.1278M. doi:10.1111/j.1365-2966.2004.07599.x.