Reconstruction of surfaces from a not large data set by interpolation

Many papers discuss the problem of recovering a function when a set of data is known on a domain $\Omega\subset {\cal R}^2$. Most of these papers assume that the size of the data set is large. At our knowledge, little or practically nothing is said about the case in which the sample has a size that is moderate. In this paper we tackle this problem. We indicate a way for its solution and hence we give a concrete example. Some numerical experiments are shown.