Handa BK, Land AC, Lord JA, Morgan BA, Rance MJ, Smith CF (April 1981). "Analogues of β-LPH61–64 possessing selective agonist activity at μ-opiate receptors". European Journal of Pharmacology. 70 (4): 531–40. doi:10.1016/0014-2999(81)90364-2. PMID6263640.
Handa BK, Land AC, Lord JA, Morgan BA, Rance MJ, Smith CF (April 1981). "Analogues of β-LPH61–64 possessing selective agonist activity at μ-opiate receptors". European Journal of Pharmacology. 70 (4): 531–40. doi:10.1016/0014-2999(81)90364-2. PMID6263640.