Leedy, P. D. (2005). Practical research planning and design Paul D. Leedy, Jeanne Ellis Ormrod. Pearson Educatin.
Lua i Stíl Chicago (17ú heag.)Leedy, Paul D. Practical Research Planning and Design Paul D. Leedy, Jeanne Ellis Ormrod. Pearson Educatin, 2005.
Lua MLA (8ú heag.)Leedy, Paul D. Practical Research Planning and Design Paul D. Leedy, Jeanne Ellis Ormrod. Pearson Educatin, 2005.
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