"In the mid-twentieth century, John Knox introduced a variation on the Semler Hypothesis that combined it with elements of the other two hypotheses Patristic and Schwegler": he considers that the gospels of Luke and Marcion date back to a common source, and that the gospel of Marcion removed parts of this source, while that Luke added some parts not originally present in this source. This hypothesis was developed further by Joseph B. Tyson. Knox and Tyson also studied the Book of Acts, and "oth find an anti-Marcionite intent behind the handling of Paul in Acts."