Eli Ben-Sasson Russell Impagliazzo Avi Wigderson Near-Optimal Separation of Treelike and General Resolution Electronic Colloquium on Computational Complexity (ECCC) 2000 7 5 db/journals/eccc/eccc7.html#ECCC-TR00-005 http://eccc.hpi-web.de/eccc-reports/2000/TR00-005/index.html