Dear Sirs:
A typo has occurred in the original post,
Correction:
Define(Pi(H(d))) by recursion:
For every ordinal d
Pi(H(d))=H(d)for i=0
Pi(H(d))=P(Pi-1(H(d))) for any successor ordinal i
Pi(H(d))=Union(j<i) Pj(H(d)) for any limit ordinal i
were "P" stands for "power set".
Best Regards
Zuhair