APA (7th ed.) Citation

Checkland, P. (1999). Soft systems methodology: A 30-year retrospective. John Wiley.

Chicago Style (17th ed.) Citation

Checkland, Peter. Soft Systems Methodology: A 30-year Retrospective. Chichester, New York: John Wiley, 1999.

MLA (9th ed.) Citation

Checkland, Peter. Soft Systems Methodology: A 30-year Retrospective. John Wiley, 1999.