During the course of Helmut Maier’s six-year study of GDCh’s Nazi history, he consulted more than 20,000 pages of documents, including 10,000 pages of documents at the Bayer archive in Leverkusen 5,000 pages of documents in the GDCh archive 4,000 to 5,000 pages from the Berlin government archive 1,000 pages from a Russian archive in Moscow Nearly 1,000 pages from a former IG Farben photochemical plant SOURCE: Helmut Maier

https://cen.acs.org/articles/91/i37/Chemistry-Nazi-Germany.html