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This article is presented in two parts. The first part is a study of the
term "Tabaseyn" in the historical and geographical texts - from the 3rd century up to now. Through reliance on the sources, the author has come to the conclusion that prior to the 6th century A.H., Tabaseyn (the two Tabases) was not applied to Tabas-e _orma-and Tabas-e 'Annan which were later mentioned as Tabas-e Gilaki and Tabas-e
Maslnan. Since the 6th century both Arab geographers and more recent scholars have referred to Tabas-e Gilaki and Tabas-e Masinan as "Tabaseyn".















In the second part of this article, by analizing the historians' views, following the Muslims' route from Kerman to Korasan and by studying the locations and distance between Tabas-e Gilakiand Tabas-e Masinan, the author has come to the conclusion that what is meant by Tabaseyn is Tabas-e Giiaki and Tabas-e korin. And in the early Hegira centuries, KorIn, at least as a city, was like Tabas-e Gilakl. the evidence and indications that reveal the historical background of Korin confirm the author's view.