42In the first place, it must be borne in mind that the obligation to state reasons, provided for in Article 296 TFEU, is an essential procedural requirement, as distinct from the question whether the reasons given are correct, which goes to the substantive legality of the contested measure. With that in mind, the statement of reasons must be appropriate to the act at issue and must disclose in a clear and unequivocal fashion the reasoning followed by the institution which adopted the measure in question in such a way as to enable the persons concerned to ascertain the reasons for the measure and to enable the competent court to exercise its power of review (judgment of 29 September 2011, Elf Aquitaine v Commission, C‑521/09 P, EU:C:2011:620, paragraphs 146 and 147).