Fisher, Nicholas I.; Hall, Peter; Kirk, David J. - In: Journal of Multivariate Analysis 59 (1996) 2, pp. 217-229
Much of the practical interest attached to curves and surfaces derives from features of roughness, rather than smoothness. For example, considerable attention has been paid to fractal models of curves and surfaces, for which the notions of a normal and curvature are usually not well defined....
