@article {Knotters1995Geoderma,
	title = {{A comparison of kriging, co-kriging and kriging combined with regression for spatial interpolation of horizon depth with censored observations}},
	journal = {Geoderma},
	volume = {67},
	number = {3-4},
	year = {1995},
	pages = {227-246},
	author = {Knotters, M. and Brus, D.~J. and Voshaar, J.~H.~O.}
}