Polygons Flip Finitely: Flaws and a Fix
Erik D. Demaine, Blaise Gassend, Godfried T. Toussaint · Smith ScholarWorks (Smith College) · 2006
Every simple planar polygon can undergo only a finite number of pocket flips before becoming convex. Since Erdős posed this as an open problem in 1935, several independent purported proofs have been published. However, we uncover a plethora of errors and gaps in these arguments, and remedy these problems with a new (correct) proof.