1. Coifman, R., Lions, P.L., Meyer, Y., Semmes, S.: Compensated compactness and Hardy spaces, J. Math. Pures Appl. 72, 247–286 (1993)
2. De Lellis, C., Müller, S.: Optimal rigidity estimates for nearly umbilical surfaces, to appear in J. Diff. Geom.
3. Fefferman, C., Stein, E.M.: ℋ p spaces of several variables, Acta Math. 129, 137–193 (1972)
4. Müller, S., Šverák, V.: On surfaces of finite total curvature, J. Diff. Geom. 42(2), 229–258 (1995)