1 . EUROPEAN COMMUNITIES - OWN RESOURCES - SYSTEM - PRINCIPLES - EQUALITY OF TREATMENT ( EEC TREATY , ART . 201 ; COUNCIL DECISION OF 21 APRIL 1970 ) 2 . EUROPEAN COMMUNITIES - OWN RESOURCES - EXPORT REFUNDS WRONGLY MADE - REPAYMENT - DISPUTES - JURISDICTION OF THE NATIONAL COURTS - REQUIREMENT OF CO-OPERATION ( EEC TREATY , ART . 5 ; REGULATION NO 729/70 OF THE COUNCIL , ART . 8 ) 3 . EUROPEAN COMMUNITIES - OWN RESOURCES - EXPORT REFUNDS WRONGLY MADE - REPAYMENT - APPLICATION OF NATIONAL LAW - PRINCIPLE OF LEGAL CERTAINTY - APPLICABILITY - CONDITIONS ( REGULATION NO 1957/69 OF THE COMMISSION , ART . 6 ( 5 ))