Work based on symbolic manipulations \bibitem {rcc2} X. S. Gao \& S. C. Chou Solving Geometric Constraint Problems, II. A Symbolic Approach and Decision of Rc-constructibility, \bibitem{kondo} K. Kondo, Algebraic method for manipulation of dimensional relationships in geometric models, {\it Geometric Aided Design}, 24(3), 141-147, 1992. \bibitem{buch} S A. Buchanan and A. de Pennington, Constraint Definition System: A Computer-Algebra Based Approach to Solving Geometric-Constraint Problems, {\it Geometric Aided Design}, 25(12), 141-147, 1993.