1. Callender, E. D., Hölder continuity of N-dimensional quasiconformal mappings. Pacific J. Math. 10, 499?515 (1960)
2. Courant, R., Dirichlet's principle. New York: Interscience publishers 1950
3. Eells, J., & J. H. Sampson, Harmonic mappings of Riemannian manifolds. Am. J. of Math. 86, 109?160 (1964)
4. Gehring, F. W., The Caratheodory convergence theorem for quasi conformal mappings in space. Ann. Ac. Sci. Fenn. A, 336/II, 1?21 (1963)
5. Lelong-Ferrand, J., Représentation conforme et transformations à intégrale de Dirichlet bornée. Paris: Gauthier Villars 1955