@article {Guth1995ZG,
	title = {{Slope and aspect calculations on gridded digital elevation models: Examples from a geomorphometric toolbox for personal computers}},
	journal = {Zeitschrift f{\"u}r Geomorphologie},
	volume = {101},
	year = {1995},
	pages = {31-52},
	author = {Guth, P.~L.}
}