Diagnosis
You want to reference a reservation document which was posted in adifferent controlling area. This is not possible; the two documentsmust be in the same controlling area.
The error may be due to the fact that the document you are currentlyworking on is assigned to a controlling area, but the reservationdocument is not (or vice versa).

System Response

Procedure
Enter a reference document which is in the same controlling area as thedocument you are currently working on.