Action to annul an arbitral award. Failure to comply with the arbitrator's duty of disclosure (Article 14, § 1º, of the Brazilian Arbitration Act). Arbitral tribunal that omitted to disclose acquaintance with the lawyers of one of the parties when, in fact, they had previously participated together in several arbitration-related events, served together on examination panels for academic papers authored by those lawyers, and co-authored books. Nullity of the arbitral award (Article 32, II, of the Brazilian Arbitration Act):