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Manral, L.; Gupta, P.K.; Ganesan, K.; Malhotra, R.C., Gas chromatographic retention indices of fentanyl and its analogues, J. Chromatogr. Sci., 2008, 46, 7, 551-555, https://doi.org/10.1093/chromsci/46.6.551 . [all data]