The Bible contains two books that are usually called apocalypses: Daniel (especially chapters 2, 7-12) and Revelation. There are also several sections of books that some scholars label apocalypses; examples are Isaiah 24-7, the visions in Zechariah i-8; and the Synoptic Apocalypse (Mark 13 with parallels in Matthew 24 and Luke 21). The nature of these literary units as divine disclosures of what is destined to take place sets them off from other scriptural books and has gained for them a certain popular and scholarly fascination. Their concern with the future has led more literal readers to mine the texts for clues to when the end will be and what signs will mark its approach; modern apocalyptic groups have joined a series of predecessors in this effort. The potential dangers of a literal reading have caused some uneasiness, especially about the book of Revelation in Christian history. So much has this been the case that its place in the New Testament was denied by some already in antiquity. In recent times scholars have devoted large amounts of time to clarifying obscure points in Daniel and Revelation and to studying them in connection with other, extra-biblical works that appear to belong to the same literary category.