van Dam, Edwin R. “The Spectral Excess Theorem for Distance-Regular Graphs: A Global (Over)view”. The Electronic Journal of Combinatorics 15, no. 1 (October 13, 2008): R129. Accessed March 28, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v15i1r129.