@article{MR_1988_34_a1,
     author = {V. A. Kostova},
     title = {An exact estimate for approximation of a class of convex functions by {Szasz-Mirakian} operators in {L_1} norm},
     journal = {M\ensuremath{\alpha}\ensuremath{\theta}\ensuremath{\eta}\ensuremath{\mu}\ensuremath{\alpha}\ensuremath{\tau}\ensuremath{\iota}\ensuremath{\kappa}\ensuremath{\acute\eta} E\ensuremath{\pi}\ensuremath{\iota}\ensuremath{\theta}\ensuremath{\varepsilon}\ensuremath{\acute\omega}\ensuremath{\rho}\ensuremath{\eta}\ensuremath{\sigma}\ensuremath{\eta}},
     pages = {5--12},
     year = {1988},
     volume = {34},
     language = {gr},
     url = {http://geodesic.mathdoc.fr/item/MR_1988_34_a1/}
}