Some of these principles are expressly stated in the Convention. This is the case, for example, of the principle of good faith referred to, although in a rather unusual context, in Article 7 (1) (see § 2.4., infra), the principle of the parties' autonomy (Article 6), the rule that the agreement between the parties is not subject to any formal requirement (Articles 11 and 29 (1)), the principle according to which any notice or other kind of communication made or given after the conclusion of the contract becomes effective on dispatch (Article 27) and the rule that delay in payment creates an obligation to pay interest on the sum in arrears (Article 78).