Fowler, F. J., & Floyd J. Fowler; Jr. Survey research methods. Thousand Oaks, Calif: Sage Publications.

Fowler, Floyd J., و Floyd J. Fowler; Jr. Survey Research Methods. Thousand Oaks, Calif: Sage Publications.

Fowler, Floyd J., و Floyd J. Fowler; Jr. Survey Research Methods. Thousand Oaks, Calif: Sage Publications.