Harper Lee's sister says the author of To Kill a Mockingbird has indeed co-operated with a memoir about her. And the publisher has set a release date: fall 2013.

The law firm Barnett, Bugg, Lee & Carter had released a signed  statement last month from Harper Lee disputing an announcement by Penguin Press that Marja Mills' The Mockingbird Next Door had been written with "full access" to the media-shy novelist.

But Alice Lee, Harper Lee's sister, is a partner in the firm and said in a signed letter dated May 21 and released Monday by Penguin that the statement was prepared without her knowledge and "does not represent" the feelings of either sister.

A woman who answered the phone at Barnett, Bugg declined comment and hung up on a reporter seeking comment.