So how do you know what's in them if they're locked away and secret?

Do what investigative Journalists working for German ZDF TV channel did and and
do a research Jonastal/Kammler, U-235 documents as well as the Journal pages of
89.Infantary division between 4/8/45 1,35PM and 4/11/45 7,35 PM under freedom
of information act.They are all still classified.