1. Linear Operators and Approximation Theory;Korovkin,1960
2. Bernstein Polynomials;Lorentz,1953
3. Sur l'approximation des fonctions convexes d'ordre supérieur;Popiviciu;Mathematica (Cluj),1935
4. The degree of convergence of sequences of linear positive operators;Shisha,1968
5. The degree of approximation to periodic functions by linear positive operators;Shisha;J. Approximation Theory,1968