@article{SMJ2_2021_46_3_a4,
     author = {Draganov, Borislav},
     title = {Strong converse inequalities for the weighted simultaneous approximation by the {Sz\'asz-Mirakjan} operator},
     journal = {Serdica Mathematical Journal},
     pages = {261--286},
     publisher = {mathdoc},
     volume = {46},
     number = {3},
     year = {2021},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SMJ2_2021_46_3_a4/}
}