1. Motion by curvature of planar networks;Mantegazza;Ann. Sc. Norm. Super. Pisa Cl. Sci. (5),2004
2. The four-vertex theorem revisited—two variations on the old theme;Tabachnikov;Amer. Math. Monthly,1995
3. Minimax Methods in Critical Point Theory with Applications to Differential Equations;Rabinowitz,1986