Barker has familiarized himself with dozens of manuscript witnesses in Latin, Dutch, German, English, and Italian dialects from microfilms and digital images, many of them unpublished. This is a huge step toward having an informed discussion about extant medieval Western harmony sources and their filiation. Barker is to be praised and applauded for making this effort. * Ulrich B. Schmid, Kirchlichen Hochschule Wuppertal/Bethel, Review of Biblical Literature * Barker's study takes the field in exactly the direction I have envisioned it should go. In just a matter of years, Barker has produced a tour-de-force that I had imagined it would take a lifetime to complete. All future research on the Diatessaron, including my own, will refer back to this seminal study. * Nicholas J. Zola, Pepperdine University, Journal of Theological Studies * Barker's work is important, especially for specialists in Diatessaronic studies. However, for those new to the discipline it is a highly important work which will make readers aware of the current state of research and the difficult and contested issues that surround this topic. As such it is a fine piece of scholarship that will, no doubt, have enduring value. * Paul Foster, University of Edinburgh, Expository Times * This careful and succinct study offers an important contribution to our understanding of how Tatian created his mind-boggling text, while also tracing, sometimes controversially, the twists and turns of its ongoing development and reception. * Alan Garrow, Journal for the Study of the New Testament * Barker has produced a tour-de-force that I had imagined it would take a lifetime to complete. All future research on the Diatessaron, including my own, will refer back to this seminal study. * Nicholas J Zola, Journal of Theological Studies *