Martin Aigner Zbynek Sír Bert Jüttler Least-Squares Approximation by Pythagorean Hodograph Spline Curves Via an Evolution Process. 45-58 2006 conf/gmp/2006 GMP http://dx.doi.org/10.1007/11802914_4 db/conf/gmp/gmp2006.html#AignerSJ06