Wilhelms, F. T. (1973). Supervision in a new key. Association for Supervision and Curriculum Development.
Lua i Stíl Chicago (17ú heag.)Wilhelms, Fred T. Supervision in a New Key. Washington: Association for Supervision and Curriculum Development, 1973.
Lua MLA (9ú heag.)Wilhelms, Fred T. Supervision in a New Key. Association for Supervision and Curriculum Development, 1973.
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