Hardy space estimates for bi-parameter Littlewood-Paley square functions

Suppose that g(f)are bi-parameter Littlewood-Paley square functions which were introduced by H.Martikainen.It is known that the L^2(R^n×R^m)boundedness and the H1(R^n×R^m)-L1(R^n×R^m)boundedness of g(f)have been proved by H.Martikainen and by Z.Li and Q.Xue,respectively.In this paper,we apply the vector-valued theory,the atomic decomposition of product Hardy spaces,and Journe’s covering lemma to show that g(f)are bounded from H^p(R^n×R^m)to Lp(R^n×R^m)with p smaller than 1.