Finally I got the book “In Zeppelin over Switzerland”, released in 1930 by Orell Füssli. There are 55 Zeppelin photos over Switzerland. But these photos were made in 1929, one year before the landing in Berne. It’s not as big as I expected. But nevertheless, it’s a very rare book, and as far as I know, it’s the only Zeppelin book about Switzerland. And in the national libray of Berne, it’s only for reference.