y=0(1q2ya2)(a2,(ab)1;q)y(1a2)(q,bqa1;q)y(ba1)yqy2Qn(12(aqy+a1qy);a,b|q1)Qm(12(aqy+a1qy);a,b|q1)=(qa2;q)(ba1q;q)(q,(ab)1;q)n(ab)nqn2δn,m.