Judgment of the Court of 26 October 1999 in Case C-294/97 (reference for a preliminary ruling from the Finanzgericht Münster): Eurowings Luftverkehrs AG v Finanzamt Dortmund-Unna (Freedom to provide services — Trade tax — Add-back to the taxable amount — Exemption inapplicable to the lessee where the proprietor of the goods leased is established in another Member State and is therefore not liable to the tax)