In 1977, George Howard propounded in the scholarly "Journal of Biblical Literature" his theory that "towards the end of the first century" (when the were still appearing) Christians had already begun to use "nomina sacra" in place of the Tetragrammaton. While in non-biblical material Jews freely used either the Tetragrammaton or a substitute such as κύριος, in copying the biblical text itself they carefully guarded the Tetragrammaton, a practice that they extended to translation into Greek but not into Aramaic (p. 72); but, Howard said, in the earliest extant copies of the Christian LXX the tetragrammaton is not to be found and is almost universally replaced by κύριος (p. 74). "In all probability", he said, "the Tetragram in the Christian LXX began to be surrogated with the contracted words and at least by the beginning of the second century" (pp. 74−75). "Towards the end of the first century", he said, "Gentile Christians [...] substituted the words κύριος and θεός [...] for the Tetragram" (pp. 76−77). Howard's theory was that, in the interval between the writing of the texts that were later compiled to form the New Testament and the adoption of these surrogates, quotations in those texts would have the Tetragrammaton: "It is reasonable to believe that the NT writers, when quoting from Scripture, preserved the Tetragram within the biblical text. On the analogy of pre-Christian Jewish practice we can imagine that the NT text incorporated the Tetragram into its OT quotations and that the words κύριος and θεός were used when secondary references to God were made in the comments that were based upon the quotations. The Tetragram in these quotations would, of course, have remained as long as it continued to be used in the Christian copies of the LXX. But when it was removed from the Greek OT, it was also removed from the quotations of the OT in the NT. Thus somewhere around the beginning of the second century the use of surrogates must have crowded out the Tetragram in both Testaments" (p. 77).