Babbie, E. R. (1990). Survey research methods (2nd ed.). California.
Lua i Stíl Chicago (17ú heag.)Babbie, Earl R. Survey Research Methods. 2nd ed. Belmont: California, 1990.
Lua MLA (9ú heag.)Babbie, Earl R. Survey Research Methods. 2nd ed. California, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.