1. O. Bonnet, Memoire sur la theorie des surfaces applicables, J.Ec Polyt., 42(1867) 79–92.
2. S.S.Chern, Deformation of surfaces preserving principal curvatures. Differential geometry and complex analysis p.155–p.163 H.E.Rauch Memorial volume 1985.
3. R. Courant and D. Hilbert, Methods of Mathematical Physics Vol.II p.89-, 1962.
4. A.Gervasio Colares and Katsue Kenmotsu, Isometric Deformation of surfaces in R
3 preserving the Mean Curvature Function, preprint. 1987.
5. I.M.Roussos, Principal curvature preserving isometries of surfaces in ordinary space. Priprint Univ. of Minnesota 1986.