Geodesic
The approximation of continuous periodic functions of two variables by Faward sums
Matematičeskie zametki, Tome 13 (1973) no. 5, pp. 655-666.

Voir la notice de l'article provenant de la source Math-Net.Ru

An estimate is given of the magnitude of the exact upper bound of the errors of double Faward sums on classes of continuous periodic functions, and asymptotic equations are found in the case of the classes $H_{A,B}^{\alpha,\beta}$ for these quantities, expressed in terms of the exact upper bounds of the errors of Faward sums on the classes $H_A^\alpha$ and $H_B^\beta$ of functions of one variable. 
@article{MZM_1973_13_5_a3,
     author = {A. I. Stepanets},
     title = {The approximation of continuous periodic functions of two variables by {Faward} sums},
     journal = {Matemati\v{c}eskie zametki},
     pages = {655--666},
     publisher = {mathdoc},
     volume = {13},
     number = {5},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1973_13_5_a3/}
}
TY  - JOUR
AU  - A. I. Stepanets
TI  - The approximation of continuous periodic functions of two variables by Faward sums
JO  - Matematičeskie zametki
PY  - 1973
SP  - 655
EP  - 666
VL  - 13
IS  - 5
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MZM_1973_13_5_a3/
LA  - ru
ID  - MZM_1973_13_5_a3
ER  - 
%0 Journal Article
%A A. I. Stepanets
%T The approximation of continuous periodic functions of two variables by Faward sums
%J Matematičeskie zametki
%D 1973
%P 655-666
%V 13
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MZM_1973_13_5_a3/
%G ru
%F MZM_1973_13_5_a3
A. I. Stepanets. The approximation of continuous periodic functions of two variables by Faward sums. Matematičeskie zametki, Tome 13 (1973) no. 5, pp. 655-666. http://geodesic.mathdoc.fr/item/MZM_1973_13_5_a3/