@article{DAN_1977_236_6_a4,
     author = {M. I. Levin and Yu. M. Girshovich},
     title = {Extremal problems for cubature formulas},
     journal = {Doklady Akademii Nauk},
     pages = {1303--1306},
     publisher = {mathdoc},
     volume = {236},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_236_6_a4/}
}