Venkatesan Guruswami Daniel Lewin Madhu Sudan Luca Trevisan A tight characterization of NP with 3 query PCPs Electronic Colloquium on Computational Complexity (ECCC) 1998 34 5 db/journals/eccc/eccc5.html#ECCC-TR98-034 http://eccc.hpi-web.de/eccc-reports/1998/TR98-034/index.html