On monotone Fourier coefficients of a function belonging to   Nikol'ski\u{\i}--Besov classes
  In this paper, necessary and sufficient conditions on terms of monotone Fourier coefficients for a function to belong to a Nikol'ski\u{\i}--Besov type class are given. 
Muharrem Q. Berisha and Faton M. Berisha
math.CA