Conti S., De Lellis C., Müller S., Romeo M..  2003.  Polyconvexity equals rank-one convexity for connected isotropic sets in $\Bbb M^{2\times 2}$.. Comptes Rendus Mathématique. Académie des Sciences. Paris. 337:233–238. PolyCRAS.pdf (149.28 KB)

De Lellis C., Müller S..  2005.  Optimal rigidity estimates for nearly umbilical surfaces.. Journal of Differential Geometry. 69:75–110. StJDG.pdf (379.65 KB) Errata-umbilical.pdf (118.13 KB)

De Lellis C., Müller S..  2006.  A $C^0$ estimate for nearly umbilical surfaces.. Calculus of Variations and Partial Differential Equations. 26:283–296. UmbC0.pdf (319.23 KB) Errata-umbilical-2.pdf (95.55 KB)