Crooks, P. ., Kottayil, S. ., Al-Ghananeem, A. ., , & Butterfield, D. . (2006). Opiate receptor binding properties of morphine-, dihydromorphine-, and codeine 6-O-sulfate ester congeners. Bioorganic & Medicinal Chemistry Letters, 16(16), 4291-5. https://doi.org/10.1016/j.bmcl.2006.05.060 (Original work published 2006)