Cita APA (7a ed.)

Drucker, P. F. (1999). Management challenges for the 21 st century. Harper Business.

Cita Chicago Style (17a ed.)

Drucker, Peter F. Management Challenges for the 21 St Century. New York: Harper Business, 1999.

Cita MLA (8a ed.)

Drucker, Peter F. Management Challenges for the 21 St Century. Harper Business, 1999.