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At the end of the 9th century, one of these students of Methodius – Naum, who had settled in Preslav, Bulgaria – is often credited, at least by supporters of glagolitic precedence, for the "creation" or wider adoption of the Cyrillic script, which almost entirely replaced Glagolitic during the Middle Ages. The Cyrillic alphabet is derived from the Greek alphabet used at that time, with some additional letters for sounds peculiar to Slavic languages (like ⟨ш⟩, ⟨ц⟩, ⟨ч⟩, ⟨ъ⟩, ⟨ь⟩, ⟨ѣ⟩), likely derived from the Glagolitic alphabet. The decision by a great assembly of notables summoned by Boris in the year 893 in favor of Cyrillic created an alphabetical difference between the two literary centres of the Bulgarian state in Pliska and Ohrid. In the western part the Glagolitic alphabet remained dominant at first. However, subsequently in the next two centuries, mostly after the fall of the First Bulgarian Empire to the Byzantines, Glagolitic gradually ceased to be used there at all. Nevertheless, particular passages or words written with the Glagolitic alphabet appeared in Bulgarian Cyrillic manuscripts till the end of the 14th century. Some students of the Ohrid academy went to Bohemia where the alphabet was used in the 10th and 11th centuries, along with other scripts. It is not clear whether the Glagolitic alphabet was used in the Duchy of Kopnik before the Wendish Crusade, but it was certainly used in Kievan Rus'.