Judgment of the Court of 21 March 2000 in Joined Cases C-110/98 to C-147/98 (reference for a preliminary ruling from the Tribunal Económico-Administrativo Regional de Cataluña): Gabalfrisa SL and Others v Agencia Estatal de Administración Tributaria (AEAT) (Meaning of national court or tribunal for the purposes of Article 177 of the EC Treaty (now Article 234 EC) — Admissibility — Value added tax — Interpretation of Article 17 of Sixth Directive 77/388/EEC — Deduction of tax paid on inputs — Activities prior to carrying out economic transactions on a regular basis)