The first clear mention and evidence of the Bulgars was in 480, when they served as the allies of the Byzantine Emperor Zeno (474–491) against the Ostrogoths. Anachronistic references about them can also be found in the 7th-century geography work "Ashkharatsuyts" by Anania Shirakatsi, where the "Kup'i Bulgar", "Duč'i Bulkar", "Olxontor Błkar" and immigrant "Č'dar Bulkar" tribes are mentioned as being in the North Caucasian-Kuban steppes. An obscure reference to "Ziezi ex quo Vulgares", with Ziezi being an offspring of Biblical Shem, is in the "Chronography of 354".