Estimates for the Convergence Rate of a Fourier Series in Laguerre–Sobolev Polynomials

Considering the approximation of $ f\in W^{r}_{L^{2}_{w}} $ ,with $ w(x)=e^{-x} $ , by the partial sums $ S_{r,r+n}(f,x) $ of the Fourier series in a systemof polynomials orthogonal in the sense of Sobolev and generated by a system of classicalLaguerre polynomials, we obtain some estimates for the convergence rate of $ S_{r,r+n}(f,x) $ to  $ f(x) $ .