Are the provisions of Articles 167, 168, 178 and 179 of the VAT Directive to be interpreted to the effect that the revenue authority is required to recognise, in the course of a tax audit, a taxable person's right of deduction in circumstances in which, although there is no indication in the taxable person's VAT return of the tax paid, the taxable person possesses invoices consistent with that directive and, during the audit, requests recognition of its right of deduction?