อ้างอิง ของ ปฏิทินกริกอเรียน

Blackburn, B. & Holford-Strevens, L. (1999). The Oxford Companion to the Year. Oxford University Press ISBN 0-19-214231-3. Pages 98–99.
Coyne, G. V., Hoskin, M. A., and Pedersen, O. (Eds.) (1983). Gregorian reform of the calendar: Proceedings of the Vatican conference to commemorate its 400th anniversary, 1582-1982. Vatican City: Pontifical Academy of Sciences, Specolo Vaticano.
Duncan, D. E. (1999). Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year. Harper Perennial. ISBN 0-380-79324-5.
Gregory XIII. (2002). Inter Gravissimas (W. Spenser & R. T. Crowley, Trans.). International Organization for Standardization. (Original work published 1582)
Lee, P.H. & de Bary, W. T. (Eds., with Yongho Ch'oe & Kang, H.H.W.). (2000). Sources of Korean Tradition, (Vol. 2). New York: Columbia University Press, 2000.
Moyer, G. (May 1982). "The Gregorian Calendar". Scientific American", pp. 144–152.
Online Etymology Dictionary retrieved 23 August 2006
Seidelmann, P. K. (Ed.). (1992). Explanatory Supplement to the Astronomical Almanac. Sausalito, CA: University Science Books.

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