Is it possible to generate Purchase requisition (PR) with reference to Scheduling Agreement?

PR can be created with reference to another PR and can not be created referencing a PO or Scheduling agreements. PO & Scheduling are created and controlled by purchasing organizations. PR can be created by even end users. For creating PR with reference to another PR, follow the menu path:
Purchasing->Requisition->Create.
Requisition->Copy reference and enter.
However requirement can be generated with reference to Scheduling agreement when MRP is run. For this to happen, source list has to be maintained for that item-vendor combination and the MRP shall be properly set.