1. Acar, T., Aral, A., Gonska, H.: On Szász–Mirakyan operators preserving
$$e^{2ax},$$
e
2
a
x
,
$$a>0$$
a
>
0
. Mediterr. J. Math. 14, 6 (2017).
https://doi.org/10.1007/s00009-016-0804-7
2. Aral, A., Acar, T., Cardenas-Morales, D., Garrancho, P.: Szász–Mirakyan type operators which fix exponentials. Results Math. 72(3), 1393–1404 (2017)
3. Aral, A., Inoan, D., Raşa, I.: On the generalized Szász–Mirakyan operators. Results Math. 65, 441–452 (2014)
4. Becker, M., Kucharski, D., Nessel, R.J.: Global approximation theorems for the Szász–Mirakyan operators in exponential weight spaces. In: Linear Spaces and Approximation Proceedings of Conference Oberwolfach, 1977, Birkhuser Verlag, Basel ISNM, 40, 319–333 (1978)
5. Braica, P.I., Pişcoran, L.I., Indrea, A.: Grafical structure of some king type operators. Acta Univ. Apul. 34/2013, 163–171 (2013)