Marshall, D. R. (1999). The four elements of successful management. AMACOM.
Lua i Stíl Chicago (17ú heag.)Marshall, Don R. The Four Elements of Successful Management. New York: AMACOM, 1999.
Lua MLA (9ú heag.)Marshall, Don R. The Four Elements of Successful Management. AMACOM, 1999.
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