1. Chen, Y.: Weak solutions to the evolution problem for harmonic maps into spheres. Preprint (1988)
2. Eells, J., Sampson, J.H.: Harmonic mappings of Riemannian manifolds. Ann. J. Math.86, 109?160 (1964)
3. Eells, J., Wood, R.: Restrictions on harmonic maps of surfaces. Topology15, 263?266 (1976)
4. Keller, J., Rubinstein, J., Sternberg, P.: Reaction ? diffusion processes and evolution to harmonic maps. Preprint (1988)
5. Ladyzenskaja, O.A., Solonnikov, V.A., Ural'ceva, N.N.: Linear and quasi-linear equations of parabolic type. Transl. Math. Monogr.23 (1968)