Case C-521/09 P: Judgment of the Court (Second Chamber) of 29 September 2011 — Elf Aquitaine SA v European Commission (Appeal — Agreements, decisions and concerted practices — Article 81 EC and Article 53 of the EEA Agreement — Market for monochloroacetic acid — Rules on imputing a subsidiary’s anti-competitive practices to its parent company — Presumption of the actual exercise of a decisive influence — Rights of the defence — Obligation to state reasons)