Windsor, Tara (2 October 2019). Daniel, Ute; Gatrell, Peter; Janz, Oliver; Jones, Heather; Keene, Jennifer; Kramer, Alan; Nasson, Bill (eds.). "Haase, Hugo". 1914–1918-online. International Encyclopedia of the First World War. Freie Universität Berlin. Retrieved 30 December 2023.
Mühlhausen, Walter (18 December 2015). Daniel, Ute; Gatrell, Peter; Janz, Oliver; Jones, Heather; Keene, Jennifer; Kramer, Alan; Nasson, Bill (eds.). "Social Democratic Party of Germany (SPD)". 1914–1918-online. International Encyclopedia of the First World War. Freie Universität Berlin. Retrieved 30 December 2023.
McElligott, Anthony (25 February 1928). Daniel, Ute; Gatrell, Peter; Janz, Oliver; Jones, Heather; Keene, Jennifer; Kramer, Alan; Nasson, Bill (eds.). "Workers' or Revolutionary Councils". 1914–1918-online. International Encyclopedia of the First World War. Freie Universität Berlin. Retrieved 4 January 2024.
Kruse, Wolfgang (6 May 2013). "Burgfrieden und Innenpolitik" [Burgfrieden and Domestic Policy]. Bundeszentrale für politische Bildung (in German). Retrieved 30 December 2023.
britannica.com
Angel, Pierre Robert (14 December 2023). "Eduard Bernstein". Encyclopedia Britannica. Retrieved 30 December 2023.
"Reichstagswahl 1920/22" [Reichstag Election 1920/22]. gonschior.de (in German). Retrieved 4 January 2024.
worldcat.org
search.worldcat.org
Gietinger Karl, Klaus; Roth, Heinz (2007). "Die Verantwortung der Mehrheitssozialdemokratie für die Morde der deutschen Gegenrevolution im Jahr 1919. Eine Dokumentation" [The Responsibility of the Majority Social Democrats for the Murders of the German Counter-revolution in 1919. A Documentation]. Sozial Geschichte (in German). 22: 82–102. ISSN1660-2870.