@article{IM2_2020_84_2_a1,
     author = {P. A. Borodin},
     title = {Greedy approximation by arbitrary set},
     journal = {Izvestiya. Mathematics },
     pages = {246--261},
     publisher = {mathdoc},
     volume = {84},
     number = {2},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2020_84_2_a1/}
}