Pogorelova, Lioubov, Stephanie Sheehan-Braine, Anthony John, and Nicholas Wasserman. “A Problem-Based Curriculum to Conceptually Develop the Multiplication Principle for Counting”. Journal of Mathematics Education at Teachers College 15, no. 1 (June 25, 2024): 37–43. Accessed June 30, 2024. https://journals.library.columbia.edu/index.php/jmetc/article/view/11949.