International organization — European Coal and Steel Community — Treaty establishing, Article 56 — Amendment of — Requirements of Article 95 (3) — Scope of Article 95 — Whether extending to amendments of substantive nature or limited to amendments of procedural rules governing exercise of powers by High Authority — Whether proposed amendment affected relationship of powers of High Authority to other Community institutions — Whether amendment restricted sovereign powers of Member States — Relevance of increase in levies resulting from amendment — Effect on Article 50 (2) of Treaty.