APA
De Bono E., . (1990). Six thinking hats. London: Penguin books.
Chicago
De Bono Edward, . 1990. Six thinking hats. London: Penguin books.
Harvard
De Bono E., . (1990). Six thinking hats. London: Penguin books.
MLA
De Bono Edward, . Six thinking hats. London: Penguin books. 1990.
