Weinberg, D. S.; Inturrisi, C. E.; Reidenberg, B.; Moulin, D. E.; Nip, T. J.; Wallenstein, S.; Houde, R. W.; Foley, K. M. (1988). „Sublingual absorption of selected opioid analgesics”. Clinical pharmacology and therapeutics44 (3): 335–342. PMID2458208.