Mohamed Shalaby Bert Jüttler Josef Schicho Approximate implicitization of planar curves by piecewise rational approximation of the distance function. 71-89 2007 18 Appl. Algebra Eng. Commun. Comput. 1-2 http://dx.doi.org/10.1007/s00200-006-0025-6 db/journals/aaecc/aaecc18.html#ShalabyJS07