@article{IM2_1969_3_3_a6,
     author = {S. Ya. Havinson},
     title = {A~Chebyshev theorem for the approximation of a~function of two variables by sums of the type $\varphi(x)+\psi(y)$},
     journal = {Izvestiya. Mathematics},
     pages = {617--632},
     year = {1969},
     volume = {3},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1969_3_3_a6/}
}