Case C-573/15: Judgment of the Court (Sixth Chamber) of 9 March 2017 (request for a preliminary ruling from the cour d’appel de Liège — Belgium) — État belge v Oxycure Belgium SA (Reference for a preliminary ruling — Value added tax — Directive 2006/112/EC — Article 98(2) — Annex III, points 3 and 4 — Principle of fiscal neutrality — Medical treatment using oxygen — Reduced VAT rate — Oxygen cylinders — Standard rate of VAT — Oxygen concentrators)