“…For smooth, piecewise monotonic, compact supported functions (this is the most interesting case, as stated in (Wendland, 1995;Fornefett et al, 2001;Siddiqui et al, 2009)), the first equality in the previous equation holds not only in the sense of the quadratic norm, but also punctually for each x p À x q . It is very easy to notice that the integrand in the previous equation is nonnegative: e…”