1. Aitken, A. G., 1934, “On Least—squares and Linear Combinations of Observations”, Proc. Royal Soc., Edinburgh, vol. 55, pp. 42–48.
2. Borgman, L. E., 1988, “New Advances in Methodology for Statistical Tests Useful in Geostatistical Studies”, Math Geol., Vol. 20, pp. 383–403.
3. Johnston, J. 1972, Econometric Methods, McGraw—Hill, New York, p. 437.
4. Journel, A. G., and Huijbregts, C. J., 1978, Mining Geostatistics: Academic Press, London, p. 600.
5. Quimby, W., 1986, Selected Topics in Spatial Statistical Analysis, Ph.D. Thesis: Statistics Department, University of Wyoming, Laramie, Wyoming.