1. Altomare, F., Mangino, E.M.: On a generalization of Baskakov operators. Rev. Roum. Math. Pures Appl. XLIV, 683–705 (1999)
2. Anastassiou, G.A., Gal, S.G.: Approximation by complex Bernstein-Schurer and Kantorovich-Shurer polynomials in compact disks. Comput. Math. Appl. 58(4), 734–743 (2009)
3. Anastassiou, G.A., Gal, S.G.: Approximation by complex Bernstein-Durrmeyer polynomials in compact disks. Meditterr. J. Math. 7(4), 471–482 (2010)
4. Atakut, Ç.: On the approximation of functions together with derivatives by certain linear positive operators. Commun. Fac. Sci. Univ. Ank. Ser. Phys.-Tech. Stat. 46(1–2), 57–65 (1997)
5. Baskakov, V.A.: An example of a sequence of linear positive operators in the space of continuous functions. Dokl. Akad. Nauk SSSR 113, 249–251 (1957) (in Russian)