In "Jesus Outside the New Testament" (2000), mainstream scholar Van Voorst considers references to Jesus in classical writings, Jewish writings, hypothetical sources of the canonical Gospels, and extant Christian writings outside the New Testament. Van Voorst concludes that non-Christian sources provide "a small but certain corroboration of certain New Testament historical traditions on the family background, time of life, ministry, and death of Jesus", as well as "evidence of the content of Christian preaching that is independent of the New Testament", while extra-biblical Christian sources give access to "some important information about the earliest traditions on Jesus". However, New Testament sources remain central for "both the main lines and the details about Jesus' life and teaching".