Two-weight characterization for commutators of bi-parameter fractional integrals

Let Iα→ be the bi-parameter fractional integral operator on Rn1×Rn2, Iα→(f)(x)=∫Rn1×Rn2f(y1,y2)|x1−y1|n1−α1|x2−y2|n2−α2dy,0<αi