Robert Feichtinger Matthias Fuchs Bert Jüttler Otmar Scherzer Huaiping Yang Dual evolution of planar parametric spline curves and T-spline level sets. 13-24 2008 40 Computer-Aided Design 1 http://dx.doi.org/10.1016/j.cad.2007.08.003 db/journals/cad/cad40.html#FeichtingerFJSY08