@article {Hengl2007Geoderma,
	title = {{Methods to interpolate soil categorical variables from profile observations: lessons from Iran}},
	journal = {Geoderma},
	volume = {140},
	number = {4},
	year = {2007},
	pages = {417-427},
	author = {Hengl, T. and Toomanian, N. and Reuter, H.~I. and Malakouti, M.~J.}
}