Or here are more from the historian
Jean Sedlar from Pittsburg University:
"Slavic settlement thus greatly reduced the territory available to the partially Romanized Illyrians and Thracians, who formerly had occupied a wide area in Balkans. Apparently most of this indigenous population became absorbed into the slavic flood leaving only remnant in the mountainous and largelly inaccessible terrain of Albania"
or
"Certain characteristic of these languages [he mentions Albanian, Bulgarian, Romanian, Greek etc.] which have no counterpart elsewhere suggest possible influence from the speech of Ancient Illirians and Thracians. Linguistic evidences thus suggest widespread contacts among the Balkan peoples at an early date."
East Central Europe in the Middle ages, University of Washington Press.