1. Betts, B., Burlingane, D., Fisher, G., Foley, J., Green, M., Kasik, D., Kerr, S., Olsen, D., and Thomas, J. (1987) “Goals and objectives for User Interface Software,” Computer Graphics ,vol. 21, no. 2 (April), 73.
2. Cardelli, L. (1988) “Building user interface by direct manipulation,” In: Symposium on User Interface Software ,ACM SIGGRAPH, pp. 152–166. (October) Banff, Alberta, Canada
3. Chailloux, J. (1986) Le-Lisp Version 15.2 Manuel de Reference ,INRIA, Domaine de Voluceau BP 105, Rocquencourt 78153 Le Chesnay Cedex, France.
4. Deux, O. (1989) The Story of O2 ,GIP Altair.
5. Devin, M. and Duquesnoy, P. (1988) Manuel de reference Aida version 1.2 ,ILOG, 2, Avenue Gallieni -94250 Gentilly, France.