Order of the Court of Justice (Fourth Chamber) of 1 April 2004 in Case C-184/03 (reference for a preliminary ruling from the Landesgericht für Zivilrechtssachen Wien): Helmut Fröschl v Republik Österreich (Article 104(3) of the Rules of Procedure — Proof of competence required in order to exercise a profession — Equivalent — Conditions — Professional experience acquired in another Member State — Principle of non-discrimination — Freedom of establishment — Freedom to provide services)