Miriam Nancy Shields, "The new calendar of the Eastern churches", Popular Astronomy32 (1924) 407–411 (page 411). This is a translation of M. Milankovitch, "The end of the Julian calendar and the new calendar of the Eastern churches", Astronomische Nachrichten No. 5279 (1924).
(Inggris) Holweck, F. (1909) (1913). "Easter". Dalam Herbermann, Charles. Catholic Encyclopedia. New York: Robert Appleton Company. Diakses tanggal 19 Februari 2009.