@article {Brus2007Geoderma,
	title = {{Optimization of sample patterns for universal kriging of environmental variables}},
	journal = {Geoderma},
	volume = {138},
	number = {1-2},
	year = {2007},
	pages = {86-95},
	author = {Brus, D.~J. and Heuvelink, G.~B.~M.}
}