TheauthorsstudythesingularintegraloperatorTΩ,αf(x)=p.v.∫R^nb(|y|Ω(y′)|y|^-n-αf(x-y)dy,definedonalltestfunctionsf,wherebisaboundedfunction,α＞0,Ω(y′)isanintegrablefunctionontheunitsphereS^n-1satisfyingcertaincancellationconditions.Itisprovedthat,forn/(n+α)＜p＜∞,TΩ,αisaboundedoperatorfromtheHardy-SobolevspaceH^pαtotheHardyspaceH^p.TheresultsanditsapplicationsimprovesometheoremsinapreviouspaperoftheauthorandtheyareextensionsofthemaintheoremsinWheeden'spaper(1969).TheproofisbasedonanewatomicdecompositionofthespaceH^pαbyHan,PaluszynskiandWeiss(1995).Byusingthesameproof,thesingluarintegraloperatorswithvariablekernelsarealsostudied.
