Michael Langberg Amir Pnueli Yoav Rodeh The ROBDD Size of Simple CNF Formulas. 363-377 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2860&spage=363 2003 conf/charme/2003 CHARME db/conf/charme/charme2003.html#LangbergPR03