References
- Babbie E 1983 The Practice of Social Research 3rd edn 359 424 Belmont, CA Wadsworth
- Dillman D 2000 Mail and Internet Surveys 2nd edn New York Wiley
- Norusis MJ 1986 The SPSS Guide to Data Analysis 233 251 Chicago, IL SPSS, Inc
- Salant P Dillman D 1994 How To Conduct Your Own Survey 10 55 New York Wiley