Other notable groups of peoples and tribes of Southeastern Europe organised themselves in large tribal unions such as the Thracian Odrysian kingdom in the east of Southeastern Europe in the 5th century BC. By the 6th century BC the first written sources dealing with the territory north of the Danube appear in Greek sources. By this time the Getae (and later the Daci) had branched out from the Thracian-speaking populations.
