References
- Spline Smoothing and Nonparametric Regression Eubank,R.L.
- Applied Nonparametric Regression Hardle,W.
- Smoothing Techniques with Implementation in S Hardle,W.
- Density Estimation for Statistics and Data Analysis Silverman,B.W.
- Kernel Smoothing Wand,M.P.;Jones,M.C.