Areal-valuedfunctionf(x)onЖbelongstoZygmundclassA.(Ж)ffitsZygmundnorm‖f‖x=inf,|f(x+t)-2f(x)+f(x-t)/t|isfinite.Itisprovedthatwhenf∈A*(Ж),thereexistsanextensionF(z)offtoH={Imz>0}suchthat‖Э^-F‖∞≤√—1+53^2/72‖f‖z.Itisalsoprovedthatiff(0)=f(1)=0,thenmax,x∈[0,1]|f(x)|≤1/3‖f‖x.
数学年刊：B辑英文版
1995年3期
