1. Constructive Approximation;DeVore,1993
2. Strong converse inequalities;Ditzian;J. Anal. Math.,1993
3. Moduli of Smoothness;Ditzian,1987
4. K-functionals and weighted moduli of smoothness;Ditzian;J. Approx. Theory,1990
5. A new characterization of weighted Peetre K-functionals;Draganov;Constr. Approx.,2005