Vikraman Arvind Jacobo Torán Solvable Group Isomorphism is (almost) in NP\cap coNP Electronic Colloquium on Computational Complexity (ECCC) 2004 008 db/journals/eccc/eccc11.html#ECCC-TR04-008 http://eccc.hpi-web.de/eccc-reports/2004/TR04-008/index.html