page 139 THE TEXT OF AMOS
We concede at the outset that our point of departure is the Masoretic Text of the book of Amos. We have studied other versions of Amos, including the Septuagint, the Peshitta, the Vulgate, and the Targum, as well as materials from Qumran and other ancient caves, and we have cited and discussed alternate readings when these had some plausibility and interest. We have also tried to deal seriously and constructively with the numerous emendations and improvements in the Hebrew text proposed by colleagues and predecessors. Time, reflection, and reconsideration have eroded the appeal and value of many of the latter, while the few that have survived and warrant discussion are dealt with in the course of the COMMENTS. For the most part, however, we find no serious alternative to the Masoretic Text, and with the few exceptions noted have clung firmly to the MT, difficult and problematic as it may be in numerous places.
We have not been overly sympathetic with efforts to remake the text in the interests of different theories about its evolution over the centuries, not because we believe that the text has come to us directly from the hands of Amos and his disciples or that it has been miraculously preserved from error (although its transmission is remarkable in many ways and for many reasons), but because we remain unconvinced by the results of the numerous scholarly undertakings. We admire both the courage and the creative energy of those who have devoted much time and strenuous effort to the quest for the earlier stages in the composition and copying of the book of Amos and to the recovery of the pristine original; but we have concentrated our own efforts on the final product, chiefly because with minor variations that is what we have and that inevitably and invariably is where we must all begin. Where we end is another matter.

The following are abridged due to length, with every intention of fairly portraying the authors' statements. Bold emphasis again is mine. caf
pages 141-144 AUTHENTIC AMOS AND LATER ADDITIONS
Since the basic work of B. Duhm and J. Wellhausen, certain passages and phrases in the book of Amos have been marked off as not the work of the prophet himself... being added quite late in its literary development. T. K. Cheyne, W. R. Harper, and S. R. Driver were mainly responsible for spreading these ideas to English readers, and George Adam Smith popularized them, making such observations respectable even for preachers.
Each scholar has his own list, for there is no surefire technique for distinguishing authentic Amos from the additions of later scribes; and each investigator arrives at his conclusions with various degrees of confidence, ranging from "perhaps" to dogmatic certainty...
A full list of passages that have been questioned by someone or other at one time or another would be quite long... For many writers in recent years the questions are settled, and it has been enough to refer to the great names of the past as warrant for repeating their conclusions. At most the reasons for doubting the authenticity of these passages are given in a summary and desultory manner.
The most common grounds are historical, literary, or theological...
...
Some arguments - partly historical, partly literary, partly theological - depend on the results of research into other parts of the Bible...
Arguments, mainly literary, deny to Amos compositions that do not belong to any of the standard prophetic genres...
... In this, as in many similar problems, the arguments become very attentuated indeed. And when more emendations are required to fill in the cracks, the credibility of the result recedes even further.
We recognize that no one can "prove" that these verses (or any other parts of the book for that matter) did or did not come from Amos himself, or from circles very close to him, which practically amounts to the same thing. We ourselves have great interest in these issues but do not believe that they can be solved either by scholarly ingenuity or by appeal to certain postulates about the nature and evolution of biblical literature. What concerns us most is the interpretation of the book of Amos as it now stands.
As long as one does not demand certainty in such things, as long as one does not affect to have attained certainty in such things, the question of the antiquity of any particular passage can always be raised; and, because the means to indubitable answers are not available, they will doubtless continue to be raised by Biblical scholars. The enterprise seems to have exhausted itself in its conduct along the lines laid down in the nineteenth century.
...If we finish with a reluctance to discard any part of the book as "certainly not Amos," it is partly because we have come to the conclusion, after working through the whole business many times and weighing all arguements, that there are no compelling reasons against accepting most if not all of the book as possibly, indeed probably (we can never say "certainly") Amos.
We have two main reasons for deviating from traditional criticism on these points. First is the cumulative demonstration of the literary coherence of all of the diverse ingredients in the whole assemblage, whihc is more than an assemblage; it is a highly structured unity. Second is the diverse and divergent (even apparently contradictory, sometimes) points of view we account for as reflecting successive phases in the prophet's career, which underwent quite substantial changes in both inner perception and declared messages.
Behind all of that we have been compelled to question the hidden foundations of the old criticism at four points essential for its results. (1) We consider the "advanced" cosmic theology of the hymns to be, in fact, not late, but primal in the faith of early Israel and quite in tune with Amos' prophetic outlook as a whole... (2) We consider the roots of eschatological thinking are also ancient... so that there is no reason to assign eschatological passage to postexilic times just because they are eschatological. (3) We consider it to be far from demonstrated that (apparently) fulfilled prophecies could only have been composed after the events WE identify as their fulfillment... (4) We recognize the early prophets and Amos in particular, as versatile verbal craftsmen, quite capable of using cultic and wisdom pieces as well as the more direct prophetic oracles in their speeches. So form-critical identification of ingredients as nonoracular is not sufficient grounds for excising them.

Excerpts from The Anchor Bible, Amos, A New Translation with Introduction and Commentary by Francis I. Andersen and David Noel Freedman, Doubleday, copyright 1989.