Cita APA (7th ed.)

Drucker, P. F. (1999). Management challenges for the 21st century (First edition.). HarperBusiness.

Cita Chicago (17th ed.)

Drucker, Peter F. Management Challenges for the 21st Century. First edition. New York: HarperBusiness, 1999.

Cita MLA (8th ed.)

Drucker, Peter F. Management Challenges for the 21st Century. First edition. HarperBusiness, 1999.