Cyrillic script consonants from the older Glagolitic alphabet for sounds not found in Greek. Tradition holds that Cyrillic and Glagolitic were formalized either by Saints Cyril and Methodius who brought Christianity to the southern Slavs, or by their disciples. Paul Cubberley posits that although Cyril may have codified and expanded Glagolitic, it was his students in the First Bulgarian Empire under Tsar Simeon the Great that developed Cyrillic from the Greek letters in the 890s as a more suitable script for church books. Later Cyrillic spread among other Slavic peoples, as well as among non-Slavic Vlachs. Cyrillic and Glagolitic were used for
Glagolitic script If they were added by Cyril, it is likely that they were taken from an alphabet used for Christian scripture. It is frequently proposed that the letters "sha" , "tsi" , and "cherv" were taken from the letters "shin" ש and "tsadi" צ of the Hebrew alphabet, and that Ⰶ "zhivete" derives from Coptic "janja" Ϫ. However, Cubberley (1996) suggests that if a single prototype were presumed, the most likely source would be Armenian. Other proposals include the Samaritan alphabet, which Cyril learned during his journey to the Khazars in Cherson. Glagolitic letters were also used as numbers, similarly to