Ulrich B. Schmid states that "Tatian composed his armony of the canonical Gospels in Greek probably in the 60s or 70s of the second century" and use the "Gospels in the form that they had at that time". Ulrich B. Schmid claim: "in raw of chronological terms, the Diatessaron antedates virtually all the MSS of NT. Consequently the Diatessaron is of fundamental importance for the study of the text of the Gospels and for the study of the evolution of the Gospel tradition." R. F. Shedinger suggest that "Tatian preserves authentic early Gospel readings which have all disappeared from Greek manuscripts tradition, but survive in a few versional and patristic writings." Tatian's "Diatessaron" shows some variance in applying "Κύριος" to "YHWH", but this may be because of dependence on the Peshitta. R. F. Shedinger assert it must be asked if "it is possible that in the middle of the second century, Tatian had Gospels texts which consistently read "God" in Old Testament citations where the Hebrew text being cited had the Tetragrammaton, and the LXX read Κύριος? Due to variants in the titles "Lord" and "God" even in the Greek manuscripts, Professor Robert Shedinger wrote that in the Greek New Testament copies after originals it could have been changed "יהוה" by "θεος", and later by "Κύριος", and "Diatessaron" may provide additional confirmation of Howard's hypothesis: