1. ACSI: The American Customer Satisfaction Index.
http://www.theacsi.org/the-american-customer-satisfaction-index
2. Hartson, R., Pyla, P.S.: The UX Book: Process and Guidelines for Ensuring a Quality User Experience. Morgan Kaufmann, Amsterdam (2012)
3. ISO/IEC Guide 71: Guide for addressing accessibility in standards. ISO (2014)
4. ISO/IEC 25010: Systems and software engineering – Systems and software Quality Requirements and Evaluation (SQuaRE) – System and software quality models. ISO (2011)
5. ISO 9241-11: Ergonomic requirements for office work with visual display terminals (VDTs) – Part11: Guidance on usability. ISO (1998)