Shirley Halevy Eyal Kushilevitz Testing Monotonicity over Graph Products. 721-732 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3142&spage=721 2004 conf/icalp/2004 ICALP db/conf/icalp/icalp2004.html#HalevyK04