1 . MEASURE ADOPTED BY AN INSTITUTION - ADOPTION FORESEEABLE BY A PRUDENT AND DISCRIMINATING TRADER - PRINCIPLE OF LEGITIMATE EXPECTATION - INAPPLICABILITY 2 . AGRICULTURE - COMMON AGRICULTURAL POLICY - POTATOES - SUPPLY - DIFFICULTIES - REGULATIONS NOS 348/76 AND 890/76 - VALIDITY 3 . AGRICULTURE - COMMON AGRICULTURAL POLICY - POTATOES - EXPORTS TO NON-MEMBER COUNTRIES - TAX - CONVERSION INTO NATIONAL CURRENCY - EXCHANGE RATE APPLICABLE ( REGULATIONS ( EEC ) NOS 950/68 , 475/75 AND 348/76 OF THE COUNCIL )