Arnold Joseph Toynbee (15 de marzo de 1973). Constantine Porphyrogenitus and his world. Oxford University Press. ISBN978-0-19-215253-4. «A further settlement of 208,000 Slavs was planted in Bithynia (part, by then, of thema Opsikion), on the River ... The earliest piece of evidence for a deportation of Slavs from the Balkan Peninsula to Asia Minor may be a seal inscribed ... This seal is dated 'the eighth indiction', and this might be either the year 649/50 or the year 694/5. Since it is on record that 5,000 Slavs deserted from the East Romans to the Arabs as early as 664/5,1 Charanis dates the seal 650, and this dates the first deportation of Slavs from the Balkan Peninsula to Asia Minor in the reign of Constans II ...»
Lemerle, 1965. Lemerle, Paul (1965). «Thomas le Slave». Travaux et mémoires 1(en francés). Paris: Centre de recherche d'histoire et civilisation de Byzance. pp. 255-297. OCLC457007063.