@article{SM_1971_15_2_a7,
     author = {K. N. Lungu},
     title = {On best approximations by rational functions with a~fixed number of poles},
     journal = {Sbornik. Mathematics},
     pages = {313--324},
     year = {1971},
     volume = {15},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_15_2_a7/}
}