This internal document for NSA employees dated 1 March 2013 provides a guide for visiting facilities related with the OAKSTAR programme,which are largely based in the United States, save for the MONKEYROCKET source, which has information forwarded to the European Technical Center in Germany: see the Intercept article The NSA Worked To “track Down” Bitcoin Users, Snowden Documents Reveal, 20 March 2018.
This undated NSA presentation describes techniques for repurposing third party attack tools: see the Der Spiegel article The Digital Arms Race: NSA Preps America for Future Battle, 17 January 2015.
This undated presentation from the NSA’s European Cryptologic Center explains some of the activities of the agency’s main European base: see the Der Spiegel article Terrorverdächtige: NSA nutzte Erkenntnisse aus Deutschland-Filiale für Tötungen, 15 June 2014.
This internal NSA post from 16 September 2003 describes one agency staffer’s experience of working at the NSA’s German stations: see the Der Spiegel article Spying Together: Germany’s Deep Cooperation with the NSA, 18 June 2014.
This internal NSA post from 1 February 2006 describes the visit several agency personnel to bases in Germany: see the Der Spiegel article Spying Together: Germany’s Deep Cooperation with the NSA, 18 June 2014.
A listing of Sigads (Signals Intelligence Activity Designators, or collection stream associated with a signals intelligence station) based in Germany, collated by Der Spiegel. For around a dozen of the 150 or so historical sigads in this list, no closing date is supplied: see the Der Spiegel article Snowden-Dokumente: Hier sitzt die NSA in Deutschland, 18 June 2014.