Balancing the 5Es: Usability
http://www.wqusability.com/articles/5es-citj0204.pdf

Quesenbery, Whitney
Cutter IT Journal
2004

Abstract:

Just what do we mean by usability? Before we can set out to achieve it, we need to understand what it is we are trying to achieve. It's not enough to declare that from here on, our software will be more user friendly or that we will now be customer focused.