There is a new book out by Bob Bragg on this case called No Direct Evidence: The Story of the Missing Sodder Children. Have not read it but just ordered it and will read it as soon as it arrives.
No Direct Evidence: The Story of the Missing Sodder Children: Bragg, Bob Lane, Bragg, Bob Lane: 9173164504682: Amazon.com: Books
No Direct Evidence: The Story of the Missing Sodder Children: Bragg, Bob Lane, Bragg, Bob Lane: 9173164504682: Amazon.com: Books