Maureen Donnelly Barry Smith Layers: A New Approach to Locating Objects in Space. 46-60 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2825&spage=46 2003 conf/cosit/2003 COSIT db/conf/cosit/cosit2003.html#DonnellyS03