http://www.informatik.uni-trier.de/~ley/db/indices/query.html
http://scholar.google.com/advanced_scholar_search
http://hal.inria.fr/index.php?action_todo=search&s_type=advanced
http://portal.acm.org/advsearch.cfm
http://suche.suub.uni-bremen.de/en/
http://www.scirus.com/srsapp/advanced/