Sufentanil does not prolong the duration of analgesia in a mepivacaine brachial plexus block: A Dose Response Study. - Bouaziz,H.; Kinirons,B.P.; Macalou,D.; Heck,M.; Dap,F.; Benhamou,D.; Laxenaire,M-C. (Anesth Analg, 2000)