@article {Hengl2004AJSR,
	title = {{Soil sampling strategies for spatial prediction by correlation with auxiliary maps}},
	journal = {Australian Journal of Soil Research},
	volume = {41},
	number = {8},
	year = {2004},
	pages = {1403-1422},
	author = {Hengl, T. and Rossiter, D.~G. and Stein, A.}
}