Dáithí Ó hÓgáin, The Celts: A History, Cork, The Collins Press, 2002, p. 50, ISBN 0-85115-923-0. URL consultato l'8 novembre 2011.
«This, however, had little effect on the Celts, who within some years reached as far as Bulgaria. There, in 298 BC, a large body of them clashed with Cassander's army on the slopes of Mount Haemos.[…] The power of the Thracians had been reduced by the Macedonians, and now much of the area fell into Celtic hands. Many placenames of that area in ancient times bear witness to the presence of Celtic strongholds…»
