The author of the Book of Revelation identifies himself several times as "John". and states that he was on Patmos when he received his first vision. As a result, the author is sometimes referred to as John of Patmos. The author has traditionally been identified with John the Apostle to whom the Gospel and the epistles of John were attributed. It was believed that he was exiled to the island of Patmos during the reign of the Roman emperor Domitian, and there wrote Revelation. Justin Martyr (c. 100–165 AD) who was acquainted with Polycarp, who had been mentored by John, makes a possible allusion to this book, and credits John as the source. Irenaeus (c. 115–202) assumes it as a conceded point. According to the "Zondervan Pictorial Encyclopedia of the Bible", modern scholars are divided between the apostolic view and several alternative hypotheses put forth in the last hundred years or so. Ben Witherington points out that linguistic evidence makes it unlikely that the books were written by the same person.