Alexander Healy Salil P. Vadhan Emanuele Viola Using Nondeterminism to Amplify Hardness Electronic Colloquium on Computational Complexity (ECCC) 2004 087 db/journals/eccc/eccc11.html#TR04-087 http://eccc.hpi-web.de/eccc-reports/2004/TR04-087/index.html