@article{DAN_1990_315_2_a14,
     author = {V. I. Ryazanov},
     title = {On the accuracy of some convergence theorems},
     journal = {Doklady Akademii Nauk},
     pages = {317--319},
     year = {1990},
     volume = {315},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_315_2_a14/}
}