Volatile anaesthetics may be the main cause for early but not delayed postoperative vomiting: a randomized controlled trial of factorial design. - Apfel,C.C.; Kranke,P.; Katz,M.H.; Goepfert,C.; Papenfuss,T.; Rauch,S.; Heineck,R.; Greim,C.A.; Roewer,N. (Br J Anaesth, 2002)