^Winter CA, Flataker L (November 1952). "Antitussive action of d-isomethadone and d-methadone in dogs". Proceedings of the Society for Experimental Biology and Medicine. New York, N.Y.: Society for Experimental Biology and Medicine. 81 (2): 463–5. doi:10.3181/00379727-81-19912. PMID13027341. S2CID36487588.
^Portoghese PS, Poupaert JH, Larson DL, et al. (June 1982). "Synthesis, X-ray crystallographic determination, and opioid activity of erythro-5-methylmethadone enantiomers. Evidence which suggests that mu and delta opioid receptors possess different stereochemical requirements". Journal of Medicinal Chemistry. 25 (6): 684–8. doi:10.1021/jm00348a015. PMID6284938.