Analytical characterization of "etonitazepyne," a new pyrrolidinyl-containing 2-benzylbenzimidazole opioid sold online., Blanckaert, Peter, Balcaen Margot, Vanhee Celine, Risseeuw Martijn, Canfyn Michael, Desmedt Bart, Van Calenbergh Serge, and Deconinck Eric , Drug Test Anal, 2021 Sep, Volume 13, Issue 9, Number 1636, (2021)