Cita APA (7th ed.)
Kelly, J. J. (1997). The essence of logic. Prentice Hall.
Cita Chicago (17th ed.)
Kelly, John J. The Essence of Logic. New Delhi: Prentice Hall, 1997.
Cita MLA (9th ed.)
Kelly, John J. The Essence of Logic. Prentice Hall, 1997.
Atenció: Aquestes cites poden no estar 100% correctes.