Fowler, F. J. (2009). Survey research methods (4th ed.). Sage Publications.
Lua i Stíl Chicago (17ú heag.)Fowler, Floyd J. Survey Research Methods. 4th ed. Thousand Oaks: Sage Publications, 2009.
Lua MLA (8ú heag.)Fowler, Floyd J. Survey Research Methods. 4th ed. Sage Publications, 2009.
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