One of my Sunday School classmates mentioned that his Bible had an appendix to Daniel, which included three additional chapters (13 to 15). Do you know the reason why these are excluded from most Bible versions?
The Hebrew and Aramaic texts of Daniel have been very well preserved. The Septuagint, the Greek translation of the Old Testament written in the third century B.C., includes these other chapters but they are not in the Hebrew or Aramaic texts: the Prayer of Azariah, Song of the Three Young Men, Susanna, Bel and the Dragon. These books were never accepted as inspired by the Jews and were never in their Old Testament. As well, the Dead Sea Scrolls do not contain these chapters. These were probably later additions which probably came from Egypt.