J. Bouma, Using soil survey data for qualitative land evaluation. In B.A. Stewart (Editor), Advances
in Soil Sciences, Vol. 9. Springer-Verlag, New York, (1989) 177-213.
 R. L. Donahue, R. W. Miller, and J. C. Shickluna, Soils, an introduction to soils and plant growth.
 K. J. Kim, H. Moskowitz, and M. Koksalan, Fuzzy versus statistical linear regression, Euro. J. Oper.
Res., 92 (1996) 417-434.
 B. Minasny, and A. B. McBratney, The neuro-m method for fitting neural network parametric
pedotransfer functions, Soil Sci. Soc. Am. J., 66 (2002) 352-361.
 A. L. Page, R. H. Miller, and D. R. Keeney, Methods of soil analysis, Part 2, Soil Science Society
of Ameriac, Madison, Wisconsin, (1982).
 B. Sadeghpour, and D. Gien, A goodness of fit index to reliability analysis in fuzzy model. In A.
Grmela (Editor), Advances in Intelligent Systems, Fuzzy Systems, Evolutionary Computation,
WSEAS Press, Greece, (2002).
 E. Salchow, R. Lal, N. R. Fausey, and A. Ward, Pedotransfer functions for variable alluvial soils in
southern Ohio, Geoderma, 73 (1996) 165-181.
 S. M. Taheri, Trends in fuzzy statistics, Austrian J. Stat., 32 (2003) 239-257.
 P. Wang, Fuzzy sets and its applications, Publishing House of Shanghai Science and Technology,
 R. Xu, A linear regression model in fuzzy environment, Adv. Modelling Simulation, 27 (1991) 31-
 R. Xu, and C. Li , Multidimensional least-squares fitting with fuzzy model, Fuzzy Sets and Systems,
119 (2001) 215-223.
 H. J. Zimmermann, Fuzzy set theory and its applications, Kluwer Academic, Boston, (1991).