Checkland, P. (1999). Soft systems methodology: A 30 year retrospective. John Wiley and Sons.
Citazione stile Chigago Style (17a edizione)Checkland, Peter. Soft Systems Methodology: A 30 Year Retrospective. Chichester: John Wiley and Sons, 1999.
Citatione MLA (9a ed.)Checkland, Peter. Soft Systems Methodology: A 30 Year Retrospective. John Wiley and Sons, 1999.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.