Eisenach, J., De Kock, M., & Klimscha, W. (1996). alpha(2)-adrenergic agonists for regional anesthesia - A clinical review of clonidine (1984-1995). Anesthesiology, 85(3), 655-674. https://doi.org/10.1097/00000542-199609000-00026 (Original work published 1996)