Shur, Walter. “The Last Digit of ${2n \choose n}$ and $\sum {n \choose i}{2n-2i \choose N-i}$”. The Electronic Journal of Combinatorics 4, no. 2 (November 11, 1996): R16. Accessed March 27, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v4i2r16.