Ventzislav Nikov Svetla Nikova Bart Preneel Robust Metering Schemes for General Access Structures. 53-65 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3269&spage=53 2004 conf/icics/2004 ICICS db/conf/icics/icics2004.html#NikovNP04