Apocryphal Adjective Doubtful Dubious Authenticity False.  Word Emphasize

Use the word apocryphal if you want to emphasize that a story or claim is not only probably false but also difficult to verify or find evidence for. 

Examples: But it is also probable that these apocryphal versions are based on a genuine original. 

This is the most important of all the apocryphal writings for the history of religious thought.

Originally, the Apocrypha were texts that were not included in the Bible because their authenticity could not be firmly established. Today, urban legends are often described as apocryphal because they are passed on by a “friend of a friend.”