Approximations of classes of generalized Poisson integrals by Fourier   sums in metrics of spaces $L_{s}$
  In metrics of spaces $L_{s}, \ 1\leq s\leq\infty$, we find asymptotic equalities for upper bounds of approximations by Fourier sums on classes of generalized Poisson integrals of periodic functions, which belong to unit ball of space $L_{1}$. 
A.S. Serdyuk and T.A. Stepanyuk
math.CA