The Marcionite Origin of the Fourth Gospel
Joseph Turmel was a historian who lived from 1859 to 1943. He was originally Catholic, and was ordained a priest in 1882. He became a professor at the Grand Seminary of Rennes in the same year, but was deposed from that position in 1892 when one of his pupils denounced him to his superiors. He then published a series of works on the history of Christianity, under his own name and fourteen pseudonyms. The works were prohibited and condemned by the Catholic Church as they went against the tradtional view of Christian history. Joseph Turmel himself was excommunicated and declared to be a heretic in 1930.
Among his many works was one of particular relevance to the study of Marcionism; in Le Quatrieme Evangile (published under the name Henri Delafosse) he demonstrated that much of the content of the fourth Gospel was of Marcionite origin, having been re-worked by a Catholic editor. Le Quatrieme Evangile has been translated into English by Daniel Mahar, and can be accessed via the links below.
Part I: The First Redaction of the 4th Gospel / The Wedding Feast at Cana
A Survey of the Marcionite Doctrine / Origin of the 4th Gospel
Part II: The Second Redaction of the 4th Gospel / Carnal Body of Christ / The Bread of Life