E1 A/P in Mexico: Withholding VAT or Income Tax on Voucher

Hi --

We have gotten the VAT witholding to work correctly in 9.1.  My question is:  the process creates a PV for the voucher and then two additional documents in A/P, $V and $I for the withholding which together with the PV create the correct net payment to be made to the vendor.  When looking in the Supplier Ledger, how can you determine what Vouchers go with what withhodling documents?  I don't see any information that ties them together.  Is there a localization screen that we should be using to view these transactions?  Does anyone have any suggestions?

Thank you in advance for your help!