k-Protected Vertices in Unlabeled Rooted Plane Trees. - Keith Copenhaver (Graphs Comb., 2017)

A new lower bound for deterministic pop-stack-sorting. - Morgan Bauer; Keith Copenhaver (Eur. J. Comb., 2025)

Proving a Generalized Multinomial Theorem by Coloring Set Partitions. - Keith Copenhaver; Josh Hiller (Am. Math. Mon., 2026)