Frazee 1997, hlm. 89: "The Balkan peninsula had three groups of Indo-Europeans prior to 2000 BC. Those on the west were the Illyrians; those on the east were the Thracians; and advancing down the southern part of the Balkans, the Greeks." Frazee, Charles A. (1997), World History: Ancient and Medieval Times to A.D. 1500, Barron's Educational Series, ISBN0-8120-9765-3