Caiming Zhang Feng Li Dongmei Niu Xingqiang Yang Interpolation to C<sup>1</sup> boundary conditions by polynomial of degree six. 126-131 2009 Shape Modeling International http://dx.doi.org/10.1109/SMI.2009.5170173 conf/smi/2009 db/conf/smi/smi2009.html#ZhangLNY09