REFERENCE [IS] dataname PIC picclause
For example:
   01      PART-DETAIL TYPE IS DETAIL 
               NEXT GROUP PLUS 1
           MOCKUP LINE 13
           SOURCE WS-LOCATION-CODE    GROUP INDICATE
           SOURCE WS-LAST-COUNT-MONTH
           SOURCE WS-LAST-COUNT-DAY  
           SOURCE WS-LAST-COUNT-YEAR 
           SOURCE WS-QTY-IN-STOCK
           SOURCE WS-QTY-ISSUED
           SOURCE WS-QTY-RECEIVED
           REFERENCE WS-NO-OF-SALES   PIC 9999