1. Akima, H.: On estimating partial derivatives for bivariate interpolation of scattered data. The Rocky Mountain Journal of Mathematics 14 (1), 41–52 (1984).
2. Brauner, H.: Differentialgeometrie (Differential Geometry, in German). Braunschweig: Vieweg 1981.
3. Calladine, C. R.: Gaussian curvature and shell structures. In: Gregory, J. (ed.) Mathematics of surfaces, pp. 179–196. Oxford: Clarendon Press 1986.
4. Davis, P. J.: Interpolation and approximation. New York: Dover Publications 1975.
5. do Carmo, M. P.: Differential geometry of curves and surfaces. New Jersey: Prentice Hall 1976.