Kamal Jain Mohammad Mahdian Amin Saberi Approximating Market Equilibria. 98-108 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2764&spage=98 2003 conf/random/2003 RANDOM-APPROX db/conf/random/random2003.html#JainMS03