Waddington, C. H. (1977). Tools for thought. Paladin.
Cita Chicago (17th ed.)Waddington, Conrad Hal. Tools for Thought. Paladin, 1977.
Cita MLA (9th ed.)Waddington, Conrad Hal. Tools for Thought. Paladin, 1977.
Atenció: Aquestes cites poden no estar 100% correctes.