1. Bech, M., & Kristensen, M. (2009). Differential response rates in postal and Web-based surveys in older respondents. Survey Research Methods, 3(1), 1–6.
2. Best, S. J., & Krueger, B. J. (2004). Internet data collection, Quantitative applications in the social sciences (141st ed.). Thousand Oaks, California: Sage Publications.
3. Bröhl, C., Mertens, A., Brandl, C., Mayer, M., & Schlick, C. (2013). Integration technischer Assistenzsysteme in die personenbezogene Dienstleistungserbringung—Ergebnisse einer Delphi-Studie. In: Lebensqualität im Wandel von Demografie und Technik, Berlin: VDE-Verlag, (pp. 234–238), 2013.
4. Communications in Computer and Information Science;C Bröhl,2016
5. Eysenbach, G., & Wyatt, J. (2002). Using the internet for surveys and health research. Journal of Medical Internet Research, 4(2).