Payment Release Process (2 and 3 level approval)

Dear everyone,

We are looking for documentation related for Payment Release Procees on FI-AP

This process is linked to Workflow.

I only get this manuals, but these are oriented to only one level of approval

http://help.sap.com/printdocu/core/Print46c/en/data/pdf/FIBP/FI-AP-AP-RP.pdf

Payment Release Process - ERP Financials - SCN Wiki

We need a clear procedure for two or three levels of approval

Many Thanks for your help!