CASE IN in SQL

SELECT CASE WHEN ASL_COLLECT.TRANSFOR ='BILL' THEN 'BILL' WHEN ASL_COLLECT.TRANSFOR ='ADV'
THEN 'ADVANCE' WHEN ASL_COLLECT.TRANSFOR IN ('MFEE','MAINTENANCE FEE') THEN 'MAINTENANCE FEE' END AS TRANSFOR FROM ASL_COLLECT