1. Doppelblind-Vergleichsstudie über die Wirkung von Tramadol und Buprenorphin auf die postoperativen Schmerzen;Alon;Anaesthesist,1981
2. Tramadol und Pentazocin im Klinischen Doppelblind-Crossover-Vergleich;Arend;Arzneim. Forsch.,1978
3. Long term administration of the centrally acting analgesic tramadol did not induce dependence or tolerance;Barth;Pain,1987
4. A comparison of the analgesic effect of intramuscular nalbuphine and morphine in patients with postoperative pain;Beaver;J. Pharmacol. Exp. Ther.,1978
5. Intrathecal injection of codeine, buprenorphine, tilidine, tramadol and nefopam depresses the tailflick response in rats;Bernatzky;European J. Pharmacol.,1986