antrag
Something I didn't know: you can file a research request at the Stasi Records Archive. Not only for your own file, but for topics, for research and journalism. Since last year it's part of the Bundesarchiv.
I filled in the form. Topic: "Institut für Angewandte Stochastik, Akademie der Wissenschaften; Druckerzeugnis 'Tafeln gleichverteilter Zufallszahlen, Band II', 1963–1965."
Reason for the request: I wrote "private historical research," which sounds more serious than "a lady on the phone said a weird sentence."
They say it can take months. Possibly more than a year. That's fine. I've got 250,000 digits to read in the meantime.