John of Ephesus
The earlier tribes consisted of eight primary tribes ruled by eight chiefs-in-command: the five Duolu (咄陆) tribes, and the three Nushibi (弩失毕) tribes. Syriac and Greek sources (John of Ephesus, Menander Protector) also confirmed that initially, the Western Turkic Khaganate were divided into eight tribes during Istämi's lifetime and at his death.