@article {Hunter1997GA,
	title = {{Modeling the Uncertainty of Slope and Aspect Estimates Derived from Spatial Databases}},
	journal = {Geographical Analysis},
	volume = {29},
	number = {1},
	year = {1997},
	pages = {35-49},
	author = {Hunter, G.~J. and Goodchild, M.~F.}
}