De Bono, Edward. The dog-exercising machine : a study of children as inventors / Edward de Bono. - Harmondsworth : Penguin, 1971. - 125 p. : ill., facsims. ; 20 cm. + pbk. - Penguin education . ISBN: 0140806164 (pbk) Subjects--Topical Terms: Problem solving (Child psychology)Children's art. Dewey Class. No.: 155.413