How Many Isaiah's According To The Dead Sea Scrolls?
Isaiah scrolls were the first Biblical texts found, and the
first to receive serious study. There is no hint in either
of these scrolls of a "deutero-" or "trito-Isaiah," to use
the language of modern scholarship. The advocate of two or
three "Isaiah's" may suggest that the book was put in its
present form prior to the writing of the Qumran manuscripts,
but the fact remains that our oldest pre-Christian
manuscripts bear witness to the text substantially as we
have it in our printed Hebrew Bibles."
Pfeiffer, "The Dead Sea Scrolls And The Bible" 9th ed.
(Michigan: Baker, 1981) p. 112