1[1]Lehmann KA, Kartzenberg U, Schroeder-Bark B, et al. Post-operative patient-controlled analgesia with tramadol:analgesia efficacy and minimum effective concentrations. clin J Pain, 1990,6:212～220.
2[2]Dayea P. Collart L, Desmeules J. The pharmacology of tramadol. Drugs, 1994,47(Suppl):3.
