1. The approximation by means of some linear positive operators;Lupaş,1995
2. On Peano’s form of the Taylor remainder, Voronovskaja’s theorem and the commutator of positive linear operators;Gonska,2006
3. On differences of positive linear operators;Gonska;Carpathian J. Math.,2006
4. Differences of positive linear operators and the second order modulus;Gonska;Carpathian J. Math.,2008
5. New estimates for the differences of positive linear operators