Παραπομπή σε μορφή APA (7η εκδ.)

Keys, P. (1991). Operational research and systems: The systemic nature of operational research. Plenum Press.

Παραπομπή σε μορφή Chicago (17η εκδ.)

Keys, Paul. Operational Research and Systems: The Systemic Nature of Operational Research. New York: Plenum Press, 1991.

Παραπομπή σε μορφή MLA (9th εκδ.)

Keys, Paul. Operational Research and Systems: The Systemic Nature of Operational Research. Plenum Press, 1991.