Andrea Bottino Aldo Laurentini Optimal Positioning of Sensors in 2D. 53-58 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3287&spage=53 2004 conf/ciarp/2004 CIARP db/conf/ciarp/ciarp2004.html#BottinoL04