@article{DAN_1962_147_2_a3,
     author = {I. A. Grigor'eva},
     title = {A generalization of {Bernstein{\textquoteright}s} theorem on the form of nonnegative trigonometric polynomials to the case of 
},
     journal = {Doklady Akademii Nauk},
     pages = {283--286},
     publisher = {mathdoc},
     volume = {147},
     number = {2},
     year = {1962},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1962_147_2_a3/}
}