Muttray, Axel, et al. “Urine Tropenol Ester Levels in Workers Handling Tiotropium Bromide Synthesis: Implications for Exposure Prevention and Biomonitoring”. Archives of Industrial Hygiene and Toxicology, vol. 70, no. 2, May 2019, https://doi.org/10.2478/aiht-2019-70-3206.