RT Journal Article SR Electronic T1 International Union of Pharmacology. XII. Classification of opioid receptors JF Pharmacological Reviews JO Pharmacol Rev FD American Society for Pharmacology and Experimental Therapeutics SP 567 OP 592 VO 48 IS 4 A1 Dhawan, BN A1 Cesselin, F A1 Raghubir, R A1 Reisine, T A1 Bradley, PB A1 Portoghese, PS A1 Hamon, M YR 1996 UL http://pharmrev.aspetjournals.org/content/48/4/567.abstract AB