@article{TIMM_2001_7_1_a1,
     author = {V. V. Arestov and E. E. Berdysheva},
     title = {Tur\'an's problem for positive definite functions with supports in a~hexagon},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {21--29},
     publisher = {mathdoc},
     volume = {7},
     number = {1},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2001_7_1_a1/}
}