1. Schank, R and Abelson, R PScripts, Plans, Goals and Understanding John Wiley and Sons, New York (1977)
2. Newell, A and Simon, H AHuman Problem Solving Prentice-Hall, Englewood Cliffs, NJ (1972)
3. Metamagical themas. Variations on a theme as the essence of imagination;Hofstadter;Scientific American,1982
4. Koestler, AThe Act of Creation Arkana, London (1989)
5. Boden, MThe Creative Mind Abacus, London (1990)