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Regions of the chemical structure of fentanyl described in the definition of a fentanyl‐related Substance (Fentanyl‐related substances, DEA, May 2020. https://www.deadiversion.usdoj.gov/drug_chem_info/frs.pdf (accessed February 2, 2021)) [Colour figure can be viewed at wileyonlinelibrary.com]
