Heller Robert. (2000). Peter Drucker. Dorling Kindersley.
Cita Chicago (17th ed.)Heller Robert. Peter Drucker. Delhi: Dorling Kindersley, 2000.
Cita MLA (9th ed.)Heller Robert. Peter Drucker. Dorling Kindersley, 2000.
Atenció: Aquestes cites poden no estar 100% correctes.