Zulfiqar Habib Manabu Sakai G<sup>2</sup> Pythagorean hodograph quintic transition between two circles with shape control. 252-266 2007 24 Computer Aided Geometric Design 5 http://dx.doi.org/10.1016/j.cagd.2007.03.004 db/journals/cagd/cagd24.html#HabibS07