ECSC - PRODUCTION - STEEL PRODUCTION QUOTA SYSTEM - EXCLUSION OF CERTAIN UNDERTAKINGS FROM THE GRANT OF ADDITIONAL QUOTAS BY REASON OF THE NATURE OF THE AID RECEIVED - DISCRIMINATION - ABSENCE - COMPATIBILITY WITH THE RULES ON AID ( ECSC TREATY , ART . 4 ( B ); DECISIONS NOS 2320/81 , 2177/83 , ART . 18 , AND 2748/83 )