FREY, J. H. (1983). Survey Research By Telephone / James H. Frey. Sage.
Lua i Stíl Chicago (17ú heag.)FREY, JAMES H. Survey Research By Telephone / James H. Frey. Sage, 1983.
Lua MLA (8ú heag.)FREY, JAMES H. Survey Research By Telephone / James H. Frey. Sage, 1983.
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