Tom Lyche Trygve K. Nilssen Ragnar Winther Preconditioned Iterative Methods for Scattered Data Interpolation. 237-256 2002 17 Adv. Comput. Math. 3 http://dx.doi.org/10.1023/A:1016050415412 db/journals/adcm/adcm17.html#LycheNW02