The criterion of multiple attestation or independent attestation, sometimes also referred to as the "cross-sectional method", is a type of source criticism first developed by F. C. Burkitt in 1911. Simply put, the method looks for commonalities in multiple sources with the assumption that, the more sources that report an event or saying, the more likely that event or saying is historically accurate. Burkitt claimed he found 31 independent sayings in Mark and Q. Within Synoptic Gospel studies, this was used to develop the four-source hypothesis. Multiple sources lend support to some level of historicity. New Testament scholar Gerd Theissen says "there is broad scholarly consensus that we can best find access to the historical Jesus through the Synoptic tradition." A second related theory is that of "multiple forms". Developed by C. H. Dodd, it focuses on the sayings or deeds of Jesus found in more than one literary form. Bible scholar Andreas J. Köstenberger gives the example of Jesus proclaiming the kingdom of God had arrived. He says it is found in an "aphorism (Mat.5:17), in parables (Mat.9:37–38 and Mark 4:26–29), poetic sayings (Mat.13:16–17), and dialogues (Mat.12:24–28)" and is therefore likely an authentic theme of Jesus' teaching.