The effect of continuous lumbar epidural infusion of ropivacaine (0,1 %, 0,2 % and 0,3 %) and 0,25 % bupivacaine on sensory and motor block in volunteers: a double-blind study. - Zaric,D.; Nydahl,P.A.; Philipson,L.; Samuelsson,L.; Heierson,A.; Axelsson,K. (Reg Anesth, 1996)