The term is used in two senses. It is applied first to a book or document whose contents are invested with a special authority, in virtue of which the work is called authentic. In its second sense it is used as a synonym for "genuine", and therefore means that a work really emanates from the author to whom it is ascribed. The article VULGATE explains the first sense of the word; the articles on the single books of Sacred Scripture illustrate the second.
MLA citation. Albert, Francis X.E. "Authentic." The Catholic Encyclopedia. Vol. 2. New York: Robert Appleton Company, 1907. <http://www.newadvent.org/cathen/02137a.htm>.