Eli Ben-Sasson Prahladh Harsha Sofya Raskhodnikova 3CNF Properties are Hard to Test Electronic Colloquium on Computational Complexity (ECCC) 2003 006 10 db/journals/eccc/eccc10.html#ECCC-TR03-006 http://eccc.hpi-web.de/eccc-reports/2003/TR03-006/index.html