Yana Kortsarts Guy Kortsarz Zeev Nutov Approximation Algorithm for Directed Multicuts. 61-67 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3351&spage=61 2004 conf/waoa/2004 WAOA db/conf/waoa/waoa2004.html#KortsartsKN04