BECKHARD, R. (1992). Changing The Essence. Jossey-Bass Inc.
Lua i Stíl Chicago (17ú heag.)BECKHARD, Richard. Changing The Essence. Jossey-Bass Inc, 1992.
Lua MLA (8ú heag.)BECKHARD, Richard. Changing The Essence. Jossey-Bass Inc, 1992.
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