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"Tödliche Lotus-Blüten" [Deadly Lotus Blossoms]. Der Spiegel (in German) (20/1969). 12 May 1969. Archived from the original on 16 January 2016. Retrieved 16 January 2016.
"Immer Angst" [Always afraid]. Der Spiegel (in German) (38/1970). 14 September 1970. Archived from the original on 16 January 2016. Retrieved 16 January 2016.
"Circuit". projekt-spielberg.com (in German). Projekt Spielberg GmbH & Co KG. Archived from the original on 20 January 2016. Retrieved 20 January 2016.
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