Complex sentence: In 1998, it was found that Boyer could not substantiate many of the facts about the time period in Tombstone, causing some critics to describe it as a fraud and a hoax, and the university withdrew the book from its catalog.
Split into simpler sentences: In 1998, it was found that Boyer could not substantiate many of the facts about the time period in Tombstone. Some critics described the book as a fraud and a hoax, and the university withdrew the book from its catalog.