On the convergence of double Fourier series of functions from $L_p$, $p>1$
Matematičeskie zametki, Tome 21 (1977) no. 6, pp. 777-788
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It is proved that if a function from $L_p$, $p>1$, satisfies the condition
$$
\frac1{t\cdot\tau}\int_0^t\int_0^\tau|f(x+u,y+v)-f(x,y)|\,du\,dv=O\Bigl(\Bigl[\ln\frac1{t^2+\tau^2}\Bigr]^{-2}\Bigr),
$$
then the double Fourier series of function $f$, under summation over a rectangle, converges almost everywhere.
@article{MZM_1977_21_6_a4,
author = {I. L. Bloshanskii},
title = {On the convergence of double {Fourier} series of functions from $L_p$, $p>1$},
journal = {Matemati\v{c}eskie zametki},
pages = {777--788},
publisher = {mathdoc},
volume = {21},
number = {6},
year = {1977},
language = {ru},
url = {http://geodesic.mathdoc.fr/item/MZM_1977_21_6_a4/}
}
I. L. Bloshanskii. On the convergence of double Fourier series of functions from $L_p$, $p>1$. Matematičeskie zametki, Tome 21 (1977) no. 6, pp. 777-788. http://geodesic.mathdoc.fr/item/MZM_1977_21_6_a4/