Ackoff, R. L., & Emery, F. E. (1972). On purposeful systems. Tavistock Publications.
Cita Chicago (17th ed.)Ackoff, Russell Lincoln, i F. E. Emery. On Purposeful Systems. London: Tavistock Publications, 1972.
Cita MLA (9th ed.)Ackoff, Russell Lincoln, i F. E. Emery. On Purposeful Systems. Tavistock Publications, 1972.
Atenció: Aquestes cites poden no estar 100% correctes.