Drucker, P. F. (1999). Management challenges for the 21st century. Butterworth-Heinemann.
Lua i Stíl Chicago (17ú heag.)Drucker, Peter F. Management Challenges for the 21st Century. Oxford: Butterworth-Heinemann, 1999.
Lua MLA (8ú heag.)Drucker, Peter F. Management Challenges for the 21st Century. Butterworth-Heinemann, 1999.
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