שגיאת GROUP BY

SELECT KLINE, P.PART, TQUANT/1000, REQDATE, MAX(KLINE)
INTO :KLINE, :PART, :TQUANT, :OREQDATE, :MAXKLINE
FROM PORDERITEMS POI, PART P
WHERE P.PART = POI.PART
AND POI.ORD = :ORD
AND PARTNAME = :PARTNAME
GROUP BY 1,2,3,4;

השגיאה אומרת:
PORDERITEMS.KLINE Illegal referance in the GROUP BY clause

אודה לעזרה!!!