Cita APA (7th ed.)
Ackoff, R. L., & Emery, F. E. (1972). On Purposeful Systems. Intersystems.
Cita Chicago (17th ed.)
Ackoff, Russell L., i Fred E. Emery. On Purposeful Systems. Seaside, EUA: Intersystems, 1972.
Cita MLA (9th ed.)
Ackoff, Russell L., i Fred E. Emery. On Purposeful Systems. Intersystems, 1972.
Atenció: Aquestes cites poden no estar 100% correctes.