@article {Grohmann2004Compgeosci,
	title = {{Morphometric analysis in Geographic Information Systems: applications of free software GRASS and R}},
	journal = {Computers \& Geosciences},
	volume = {30},
	year = {2004},
	pages = {1055{\textendash}1067},
	author = {Grohmann, C.H.}
}