1. Agrawal P.N., Gupta V.: On the iterative combinations of Phillips operators. Bull. Inst. Math. Acad. Sinica 18(4), 361–368 (1990)
2. Agrawal P.N., Gupta V.: On convergence of derivatives of Phillips operators. Demonstr. Math. 27(2), 501–510 (1994)
3. Agrawal P.N., Gupta V., Gairola A.R.: On derivatives of an iterative combinations of Phillips operators. Nonlinear Funct. Anal. Appl. 12(2), 195–203 (2007)
4. Berens H., Lorentz G.G.: Inverse theorems for Bernstein polynomials. J. Approx. Theory 21, 693–708 (1972)
5. Butzer, P.L.: Linear combinations of Bernstein polynomials. Canad. J. Math. 5 559–567 (1953)