@article{TIMM_2011_17_3_a14,
     author = {A. V. Efimov},
     title = {A version of the {Turan} problem for positive definite functions of several variables},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {136--154},
     publisher = {mathdoc},
     volume = {17},
     number = {3},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2011_17_3_a14/}
}