@article{etna_vol9_pp56-64, author = {Esther M. Garc{\'i}a-Caballero and Teresa E. P\'erez and Miguel A. Pi\~nar}, title = {Sobolev orthogonal polynomials: interpolation and approximation}, journal = {Electron. Trans. Numer. Anal.}, volume = {9}, year = {1999}, pages = {56--64}, }