1. Priestley MB, Chao MT: Nonparametric function fitting. J. R. Stat. Soc. B 1972, 4: 385–392.
2. Lecture Notes in Mathematics 757;T Gasser,1979
3. Gasser T, Müller HG: Estimating regression functions and their derivatives by the kernel method. Scand. J. Stat. 1984, 11: 171–185.
4. Prakasa Rao BLS: Nonparametric Functional Estimation. Academic Press, Orlando; 1983.
5. Clark RM: Nonparametric estimation of a smooth regression function. J. R. Stat. Soc. B 1997, 39: 107–113.