Jürg Eggler gives an overview of scholarly research into the background to Daniel 7 from the 19th century to the present.
Jürg Eggler, Influences and Traditions Underlying the Vision of Daniel 7:2-14: The Research from the End of the 19th Century to the Present (Orbis Biblicus et Orentalis 177; Göttingen: Vandenhoeck & Ruprecht, 2000), 55-110
[Eggler gives an overview of the background to the judgment scene, the "Ancient of days," and the "son of man" in Daniel 7:9-14 in research from the 19th-century to the present]