@inbook {,
	title = {Cumulative Viewshed Analysis: a GIS-based method for investigating intervisibility and its archaeological application},
	booktitle = {Archaeology and GIS: a European perspective},
	year = {1995},
	publisher = {Routlege},
	organization = {Routlege},
	address = {London},
	keywords = {viewshed analysis line of sight cva  landscape landscape viewshed},
	url = {http://www.soton.ac.uk/~dww/Cumulative/},
	author = {Wheatley, David},
	editor = {Lock, G. and Stancic, Z.}
}