Another name for Kyiv mentioned in history, the origin of which is not completely clear, is Sambat, which apparently has something to do with the Khazar Empire. The ''Primary Chronicle'' says the residents of Kyiv told Askold "there were three brothers Kyi, Shchek, and Khoriv. They founded this town and died, and now we are staying and paying taxes to their relatives the Khazars". In his book De Administrando Imperio, Constantine Porphyrogenitus mentions a caravan of small-cargo boats which assembled annually, and writes, "They come down the river Dnieper and assemble at the strong-point of Kyiv (Kioava), also called Sambatas".