The oxmathproblems.cls was written by Keith A. Gillow. The latest version (1.3) was released on 12/5/2020. The class is based upon the standard exam class.
For more information please see the corresponding problem sheet class FAQ page
This package establishes a simple and easy-to-use LaTeX template for Tsinghua dissertations, including general undergraduate research papers, masters theses, doctoral dissertations, and post-doc reports.