Farhad Shahrokhi Ondrej Sýkora László A. Székely Imrich Vrto Bounds for Convex Crossing Numbers. 487-495 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2697&spage=487 2003 conf/cocoon/2003 COCOON db/conf/cocoon/cocoon2003.html#ShahrokhiSSV03