Drucker, P. F. (1999). Management challenges for the 21st century. Butterworth-Heinemann.
Chicago Style aipamenaDrucker, Peter F. Management Challenges for the 21st Century. Oxford: Butterworth-Heinemann, 1999.
MLA aipamenaDrucker, Peter F. Management Challenges for the 21st Century. Butterworth-Heinemann, 1999.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.