Walter Ruttmann (English Wikipedia)

Betancourt, Michael. "Walther Ruttmann's Lichtspiel Films". Cinegraphic. Retrieved 20 August 2021. from: An Excerpt from 'The History of Motion Graphics'

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"Berlin, die Sinfonie der Großstadt & Melodie der Welt Edition Filmmuseum 39". Edition Filmmuseum Shop. Munich Film Archive, German Federal Archives, Goethe-Institut. Retrieved 20 August 2021. Lichtspiel Opus 1 1920, 11'; Opus 2 1922, 3'; Opus 3 1924, 3'; Opus 4 1925, 4'; Berlin, die Sinfonie der Großstadt 1927, 65'; Melodie der Welt 1929, 48' (EDITION FILMMUSEUM is a joint project of film archives and cultural institutions in the german-speaking part of Europe. Its ambition is to publish film works of artistic, cultural and historical value in DVD editions that both utilise the possibilities of digital media and meet the quality demands of the archival profession.)

Born, Erik (30 January 2015). "Walter Ruttmann, Wochenende (1930)". Erik Born. Retrieved 20 August 2021. Assistant Professor,... in the Department of German Studies at Cornell University

"Lotte Reiniger's Introduction to The Adventures of Prince Achmed" (PDF). Milestone Films. 2001. pp. 9–11. Archived from the original (PDF) on 22 November 2009. Retrieved 25 September 2013.

"Lotte Reiniger's Introduction to The Adventures of Prince Achmed" (PDF). Milestone Films. 2001. pp. 9–11. Archived from the original (PDF) on 22 November 2009. Retrieved 25 September 2013.

Moser, Jeffrey (1 January 1921). "Lichtspiel Opus I (1921)". Fixation Database of Film and Animation. West Virginia University. Retrieved 20 August 2021.
Moser, Jeffrey (1 January 1921). "Lichtspiel Opus II (1921)". Fixation Database of Film and Animation. West Virginia University. Retrieved 20 August 2021.
Moser, Jeffrey (1 January 1924). "Lichtspiel Opus III (1924)". Fixation Database of Film and Animation. West Virginia University. Retrieved 20 August 2021.