Christian Glaßer Aduri Pavan Alan L. Selman Samik Sengupta Properties of NP-Complete Sets Electronic Colloquium on Computational Complexity (ECCC) 2004 019 db/journals/eccc/eccc11.html#ECCC-TR04-019 http://eccc.hpi-web.de/eccc-reports/2004/TR04-019/index.html