 Sem, in contrast, classified Nanai into Upper, Central, and Lower Amur groups, each divided into a number of dialects; he counted a total of ten dialects.Among the contemporary carriers of Nanaian language (middle and lower Amur dialects), dialect levelling and mixing has occurred due to extensive population migrations and the system of teaching of Nanai language (based on the Naykhin dialect); therefore it is difficult to differentiate the dialects in contemporary language data.The Nanai language is taught in secondary schools in Russia, mainly in Nanai villages in Khabarovsk Krai.