Neuman, W. L. (1991). Social research methods: Qualitative and quantitative approaches. Allyn and Bacon.
Lua i Stíl Chicago (17ú heag.)Neuman, William Lawrence. Social Research Methods: Qualitative and Quantitative Approaches. Boston: Allyn and Bacon, 1991.
Lua MLA (8ú heag.)Neuman, William Lawrence. Social Research Methods: Qualitative and Quantitative Approaches. Allyn and Bacon, 1991.
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