Geodesic
The summation of orthogonal series by linear methods
Matematičeskie zametki, Tome 4 (1968) no. 6, pp. 697-705 
V. A. Bolgov. The summation of orthogonal series by linear methods. Matematičeskie zametki, Tome 4 (1968) no. 6, pp. 697-705. http://geodesic.mathdoc.fr/item/MZM_1968_4_6_a9/
@article{MZM_1968_4_6_a9,
     author = {V. A. Bolgov},
     title = {The summation of orthogonal series by linear methods},
     journal = {Matemati\v{c}eskie zametki},
     pages = {697--705},
     year = {1968},
     volume = {4},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1968_4_6_a9/}
}
TY  - JOUR
AU  - V. A. Bolgov
TI  - The summation of orthogonal series by linear methods
JO  - Matematičeskie zametki
PY  - 1968
SP  - 697
EP  - 705
VL  - 4
IS  - 6
UR  - http://geodesic.mathdoc.fr/item/MZM_1968_4_6_a9/
LA  - ru
ID  - MZM_1968_4_6_a9
ER  - 
%0 Journal Article
%A V. A. Bolgov
%T The summation of orthogonal series by linear methods
%J Matematičeskie zametki
%D 1968
%P 697-705
%V 4
%N 6
%U http://geodesic.mathdoc.fr/item/MZM_1968_4_6_a9/
%G ru
%F MZM_1968_4_6_a9

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

A class of linear methods is distinguished which possesses the property: each method sums almost everywhere any orthogonal series in $L_2$ if and only if a subsequence of partial sums whose indices satisfy a certain condition and do not depend on the series converges almost everywhere. Questions are considered on the exact Weyl multiplier and strong summability.