* [ ] b-spline * [ ] natural spline Reading material: * https://www.mathworks.com/help/curvefit/cscvn.html * G. Koloskov, ["Closed natural splines: An effective solution"](https://doi.org/10.1016/j.amc.2005.10.041) * E.T.Y. Lee, ["Choosing nodes in parametric curve interpolation"](https://doi.org/10.1016/0010-4485(89)90003-1)
