1. Philemon is generally accepted to be an authentic letter of Paul. The grounds for acceptance are simple; the letter is a short, mundane, and presents no difficulties for Pauline authorship in style or thought.
2. Books
3. Murray J. Harris, Colossians & Philemon (Wm. B. Eerdmans Publishing Co. 1991) W. H. Griffith Thomas, Studies in Colossians and Philemon (Kregel Publications 1986) Burton L. Mack, Who Wrote the New Testament? : The Making of the Christian Myth (San Francisco, CA: HarperCollins, 1996), pp. 143-144. Raymond Edward Brown, An Introduction to the New Testament (New York: Doubleday, 1997), pp. 502-510. Udo Schnelle, translated by M. Eugene Boring, The History and Theology of the New Testament Writings (Minneapolis: Fortress Press, 1998), pp. 143-150.

Jerome’s preface to Philemon explaining that some in his day deny Pauline authorship.