APA (7th ed.) Citation

De Bono. (1999). Six thinking hats (Revised and updated ed.). Penguin Books.

Chicago Style (17th ed.) Citation

De Bono. Six Thinking Hats. Revised and updated ed. London: Penguin Books, 1999.

MLA (8th ed.) Citation

De Bono. Six Thinking Hats. Revised and updated ed. Penguin Books, 1999.