The earliest uses of the word God in Germanic writing is often cited to be in the Gothic Bible or Wulfila Bible, which is the Christian Bible as translated by Ulfilas into the Gothic language spoken by the Eastern Germanic, or Gothic, tribes. The oldest parts of the Gothic Bible, contained in the Codex Argenteus, are estimated to be from the fourth century. During the fourth century, the Goths were converted to Christianity, largely through the efforts of Bishop Ulfilas, who translated the Bible into the Gothic language in Nicopolis ad Istrum in today's northern Bulgaria. The words "guda" and "guþ" were used for God in the Gothic Bible.