Cita APA (7a ed.)

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

Cita Chicago Style (17a ed.)

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

Cita MLA (8a ed.)

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