@article{IM2_1969_3_5_a7,
     author = {A. P. Bulanov},
     title = {On the order of approximation of convex functions by rational functions},
     journal = {Izvestiya. Mathematics},
     pages = {1067--1080},
     year = {1969},
     volume = {3},
     number = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1969_3_5_a7/}
}