Complex sentence: Many today believe that it was not written by Paul but by an associate or disciple after his death, representing what they believed was his message, so Ehrman, Ehrman, Bart D. (2004).
Split into simpler sentences: Many today believe that it was not written by Paul but by an associate or disciple after his death, representing what they believed was his message. See, for example, Ehrman, Ehrman, Bart D. (2004).