APA (7th ed.) Citation

Drucker, P. F. (1999). Management challenges for the 21st century(lost/pd). Butterworth.

Chicago Style (17th ed.) Citation

Drucker, Peter F. Management Challenges for the 21st Century(lost/pd). Oxford: Butterworth, 1999.

MLA (9th ed.) Citation

Drucker, Peter F. Management Challenges for the 21st Century(lost/pd). Butterworth, 1999.