Behmaram, Afshin, and Shmuel Friedland. “Upper Bounds for Perfect Matchings in Pfaffian and Planar Graphs”. The Electronic Journal of Combinatorics 20, no. 1 (March 24, 2013): #P64. Accessed May 1, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v20i1p64.