31.
Notices.
Except as otherwise specifically provided in this Agreement, all notices required or permitted to be given shall be in writing and shall be delivered personally or sent by registered or certified mail, postage prepaid, or by express courier, with confirmation of delivery, to Publisher (with a copy to Publisher's legal department) or Author (or Author's agent) at the address for such party given above, or at such other addresses as the parties may from time to time designate by written notice given in the manner provided herein.
For notifications of breach or a request for reversion of rights, you might consider sending your letter via registered mail.