^Russia Confirms Suspicions About Gas Used in Raid, Washington Post, 31 October 2002.
^Timperley, Christopher M.; et al. (November 2012). "Analysis of Clothing and Urine from Moscow Theatre Siege Casualties Reveals Carfentanil and Remifentanil Use". J Anal Toxicol (November/December 2012) 36 (9): 647-656. Oxford Journals. pp. 647–656. Retrieved 19 September 2015.