I've been hearing a lot of back and forth arguments between some scholars, historians, and theologians in regards to the Documentary Theory, or the theory that the Pentateuch had many authors. I know it's a very tough argument for either side however I would love to hear your opinions on this argument?
Sorry if this has been posted before!
You may want to post your question in r/AcademicBiblical. If you are interested in the topic you will find great contributions there.
Edit: this post from yesterday is about Documentary theory. It does not goes in great detail as OP was just asking for sources but I'm sure you can find what you want in that sub.
Finally a question that I feel qualified to answer! The documentary hypothesis was developed by Julius Wellhausen, a German scholar, in the 19th century. He did not only locate certain 'authors' of the pentateuch, but he crafted a scenario in which the entire Hebrew Bible came to be. He was a master scholar, as exemplified in his work, Prolegomena to the History of Israel. In it, he outlines the Documentary Hypothesis. Since then, the theory has gone under numerous redactions, but to continue the answer in this direction would lead us off track from your question.
To put it simply, no mainline scholar (i.e.: one publishing in an academic journal or through an academic press) of the Old Testament / Hebrew Bible rejects multiple authorships. That being said, however, Wellhausen's specific theory has been largely abandoned. The reason being that no one believes only four authors crafted the Pentateuch. The basics of his theory, which state that geographic region (northern kingdom vs. southern kingdom), wealth disparity, and time period, affected who wrote what at what time period.
Evidence of multiple authors hands can be seen when you come across passages, such as Chronicles 14:12, which is an editing of 2 Samuel 5:20.
Modern Biblical scholarship is indebted to Wellhausen and his documentary hypothesis. I have never come across any argument against the concept behind the Documentary Hypothesis itself except, "Moses wrote the Bible," which is never suggested nor supported by the text itself. If you would like for me to provide any further information or sources, please just let me know. I would suggest reading, Prolegomena to the History of Israel, which is free on Project Gutenberg.
Edit: Modern scholars do disagree how Wellhausen conducted his history, which is based on a Hegelian notion of progress. But this is another discussion for another day.