References: Function and Functionality
| Author & Date | Item | Publisher |
| Mountford, S, Joy (1990) | 'Tools and Techniques for Creative Design' in Laurel, Brenda (ed) The Art of Human Computer Interface Design | Addison-Wesley |
| Preece, J., Rogers, Y., Sharp, H., Benyon, D., Holland, S. and Carey, T (1994) | Human-Computer Interaction | Addison-Wesley |