++++ European Communities' own resources - Repayment or remission of import duties - Article 13 of Regulation No 1430/79 - Commission decision concerning a request submitted by a Member State - Time-limit - Commission' s practice of obtaining an extension by having the request withdrawn and re-submitted - Misuse of procedure - Illegality ( Council Regulation No 1430/79, Art . 13; Commission Regulation No 1575/80 as amended, Art . 5, second paragraph, and Art . 7 )