1. G. Mastroianni, Su una classe di operatori lineari e positivi, Rend. Acc. Sc. Fis. Mat., Napoli 48 (1980) 217-235.
2. O. Agratini, B. D. Vecchia, Mastroianni operators revisited, Facta University Series Mathematics and Informatics 9 (2004) 53-63.
3. Z. Finta, V. Gupta, Direct and inverse estimates for Phillips type operators, Journal of Mathematical Analysis and Application 303 (2005) 627-642.
4. R. Păltănea, Modified Szász-Mirakjan operators of integral form, Carpathian Journal of Mathematics (2008) 378-385.
5. V. Mihes,an, Gamma approximating operators, Creative Mathematics and Informatics 17 (2008) 466-472.