[1] Altomare, F.: 
Korovkin-type theorems and approximation by positive linear operators. Surv. Approx. Theory 5 (2010), 92-164. 
MR 2721174 | 
Zbl 1285.41012[6] Bardaro, C., Boccuto, A., Demirci, K., Mantellini, I., Orhan, S.: 
Korovkin-type theorems for modular $\Psi$-$A$-statistical convergence. J. Funct. Spaces 2015 (2015), Article ID 160401, 11 pages. 
DOI 10.1155/2015/160401 | 
MR 3310460 | 
Zbl 1327.46006[7] Bardaro, C., Boccuto, A., Demirci, K., Mantellini, I., Orhan, S.: 
Triangular $A$-statistical approximation by double sequences of positive linear operators. Result. Math. 68 (2015), 271-291. 
DOI 10.1007/s00025-015-0433-7 | 
MR 3407558 | 
Zbl 1338.40009[8] Bardaro, C., Mantellini, I.: 
Korovkin theorem in modular spaces. Ann. Soc. Math. Pol., Ser. I, Commentat. Math. 47 (2007), 239-253. 
MR 2377960 | 
Zbl 1181.41035[11] Bardaro, C., Musielak, J., Vinti, G.: 
Nonlinear Integral Operators and Applications. De Gruyter Series in Nonlinear Analysis and Applications 9. Walter de Gruyter, Berlin (2003). 
MR 1994699 | 
Zbl 1030.47003[15] Karakuş, S., Demirci, K.: 
Matrix summability and Korovkin type approximation theorem on modular spaces. Acta Math. Univ. Comen., New Ser. 79 (2010), 281-292. 
MR 2745177 | 
Zbl 1240.41065[19] Nakano, H.: 
Modulared Semi-Ordered Linear Spaces. Tokyo Math. Book Series, Vol. 1. Maruzen, Tokyo (1950). 
MR 0038565 | 
Zbl 0041.23401