@article{SM_1978_34_3_a1,
     author = {B. D. Boyanov},
     title = {The existence of optimal quadrature formulas with given multiplicities of~nodes},
     journal = {Sbornik. Mathematics},
     pages = {301--326},
     year = {1978},
     volume = {34},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1978_34_3_a1/}
}