One of the most controversial discoveries in the area of early Christianity is the Secret Gospel of Mark by Morton Smith. Smith claimed that was an authentic citation of the Secret Gospel of Mark and a previously unknown letter by Clement. Others have claimed that it is a forgery. I tend toward believing that it is a forgery, not necessarily by Smith, but at least by whoever put it in the book from which Smith discovered it. The Biblical Archaeology Society has provided a nice translation for people to check out and judge for themselves. You can find the translation for the Secret Gospel of Mark here. They also have a good free article on the “discovery” of the Secret Gospel of Mark that you can find here.