BusinessDictionary.com, s.v. "instrument", retrieved 15 May 2009: "Instrument definition". Archived from the original on 2009-04-20. Retrieved 2009-05-19..
Instrument. Oxford University Press. Archived from the original on 14 September 2020. Retrieved 26 April 2019. {{cite book}}: |work= ignored (help)
BusinessDictionary.com, s.v. "instrument", retrieved 15 May 2009: "Instrument definition". Archived from the original on 2009-04-20. Retrieved 2009-05-19..