1. United Nations Statistical Commission and Economic Commission for Europe. Conference of European Statisticians. Statistical standards and studies – No. 53. Terminology on statistical metadata. United Nations, Geneva, 2000. Available from URL: http://www.unece.org/fileadmin/DAM/stats/publications/53metadaterminology.pdf (accessed March 2012).
2. Lohr SL. Sampling: Design and Analysis. Pacific Grove, CA: Duxbury Press; 1999.
3. Dillman DA, Smyth JD, Christian LM. Internet, Mail, and Mixed-Mode Surveys: The Tailored Design Method. 3rd ed. Hoboken, NJ: John Wiley & Sons; 2009.
4. American Association for Public Opinion Research. Standard Definitions: Final Dispositions of Case Codes and Outcome Rates for Surveys, 7th edition, 2011 AAPOR. Available from URL: www.aapor.org/ (accessed March 2012).
5. Burns KE, Duffett M, Kho ME, et al. ACCADEMY Group. A guide for the design and conduct of self-administered surveys of clinicians. CMAJ 2008; 179: 245-52.