Work based on numerical computation

\bibitem{thing} A. Borning, 
The Programming Language Aspect of ThingLab,
{\it ACN Tras. on Programming Language and Systems},
Vol. 3, No.4, 353-387, 1981.

\bibitem{ge}  J. X. Ge, S. C. Chou and X. S. Gao, 
Geometric Constraint Satisfaction Using Optimization Methods,
{\it Computer Aided Design}, {\bf 31}(14),  867-879, 2000.

\bibitem{juno1} G. Nelson,
Juno, A Constraint-Based Graphics System,
{\it Computer Graphics}, Vol. 19, 1985, p.235-243.

\bibitem{juno2} A. Heydon and G. Nelson,
The Juno-2 Constraint-Based Drawing Editor,
{\it SRC Research Report 131a}, 1994.

\bibitem{lamure} 
H. Lamure and D. Michelucci,
Solving Geometric Constraints By Homotopy,
{\it IEEE Trans on Visualization and Computer Graphics}, 
{\bf 2}(1):28-34, 1996.

\bibitem{lin} V.C. Lin, D.C. Gossard and  R.A. Light,
Variational Geometry In Computer-Aided Design,
{\it Computer Graphics}, vol. 15, no. 3, 171--177, 1981.

\bibitem{l-gos} R. Light and D. Gossard,
Modification of geometric models through variational geometry,
{\it Geometric Aided Design}, 14:208-214, July, 1982.

\bibitem{serrano} D. Serrano and D.C. Gossard,
Constraint Management: in Conceptual Design, in 
{\it Knowlwdge Based Expert Systems in engineering},
eds. D. Sriram and R.A. Adey, Computational Mechanics Publications, UK.

\bibitem{sutherland} I. Sutherland,
Sketchpad, A Man-Machine Graphical Communication System,
in {\it Proc. of the Spring Joint Comp. Conference},
329--345, 1963.