Barbara Tversky Navigating by Mind and by Body. 1-10 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2685&spage=1 2003 conf/spatialCognition/2003 Spatial Cognition db/conf/spatialCognition/spatialCognition2003.html#Tversky03