The terrible secret of the police
During the time of Nazism, the Germans knew where the Jews disappear. This was not often talked about aloud, especially with foreigners. I have a bibliographic rarity - the Olympic guide to Germany in 1936 in English. From it you can learn a lot about folk dances, national cuisine and historical attractions, but nothing - about racial laws. During that Olympiad from Berlin, inscriptions were removed, defaming Jews and compromising authorities.