In some cases their ethnical relations have not yet been completely determined.
The chains of Shar, Grammos and Pindus constitute a kind of natural boundary, which does not, however, coincide with ethnical limits nor with the Turkish administrative divisions.
The chief difficulty in deciding their ethnical relations is their remarkable physical difference from the neighbouring peoples.
The overwhelming numerical superiority of the Sla y s, and the very great differences in ethnical type, belief and mythology between the IndoEuropean and the Ural-Altaic races, may have contributed to the same end.
Three main divisions, however, have been clearly determined, and these are important both on political and ethnical grounds.