Unlocking Puzzling Polygons Proof settles a wickedly prickly question about unfurling crinkly polygons. Connelly, R., E.D. Demaine, and G. Rote. Straightening polygonal arcs and convexifying polygonal cycles.
Every polygon can be untangled.
Biedl, T., et al . Cocan, R., and J. O'Rourke. Demaine, E.K., M.L. Demaine, and A. Lubiw. Polyhedral sculptures with hyperbolic paraboloids. R. Sahangi, ed.