1. Collins, R. J., Weeks, J. R.: Relative potency of codeine, methadone and dihydromorphinone to morphine in self-maintained addict rats. Naunyn-Schmiedebergs Arch. exp. path. Pharmak.249, 509?514 (1965)
2. Finnegan, J. K., Haag, H. B., Larson, P. S., Dreyfuss, M. L.: Observations on the compartive pharmacologic actions of 6-di-methylamino-4,4-diphenyl-3-heptanone (Amidone) and morphine. J. Pharmacol. exp. Ther.92, 269?276 (1948)
3. Jasinski, D. R., Nutt, J. G.: Progress report on the assessment program of the NIMH addiction research center. Proceedings of the Thirty-Fourth Committee on Problems of Drug Dependence, vol. 34, pp. 442?477 (1972)
4. Johannesson, T., Woods, L. A.: Analgesic action and brain plasma levels of morphine and codeine in morphine-tolerant, codeinetolerant and nontolerant rats. Acta pharmacol. (Kbh.)21, 381?396 (1964)
5. Misra, A. L., Mule, S. J.: Stereoselectivity and differential metabolism in vivo of dextro- and levo-methadone-1-3H. Nature (Lond.)241, 281?283 (1973)