Creswell, J. W. (1994). Research design: Qualitative & quantitative approaches. Sage.
Lua i Stíl Chicago (17ú heag.)Creswell, John W. Research Design: Qualitative & Quantitative Approaches. Thousand Oaks, California: Sage, 1994.
Lua MLA (9ú heag.)Creswell, John W. Research Design: Qualitative & Quantitative Approaches. Sage, 1994.
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