Bulatov, Andrei A., Olga Karpova, Arseny M. Shur, and Konstantin Startsev. “Lower Bounds on Words Separation: Are There Short Identities in Transformation Semigroups?”. The Electronic Journal of Combinatorics 24, no. 3 (August 25, 2017): P3.35. Accessed March 16, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v24i3p35.