++++ European Communities' own resources - Post-clearance recovery of import or export duties - Error on the part of the customs authorities arising from the use, for the purposes of calculating duties, of a purely indicative national tariff manual incorporating an anticipated reduction in duty which did not occur - Error detectable by the trader - Post-clearance recovery - Not possible to claim protection of legitimate expectations ( Council Regulation ( EEC ) No 1697/79, Art . 5(2 ) )