Klein, Mathias (June 11, 2019). "Üstra macht die alten grünen Bahnen wieder neu" [Üstra makes the old green trains like new again]. Hannoversche Allgemeine Zeitung (in German). Archived from the original on July 3, 2019. Retrieved February 21, 2020.
Klein, Mathias (June 11, 2019). "Üstra macht die alten grünen Bahnen wieder neu" [Üstra makes the old green trains like new again]. Hannoversche Allgemeine Zeitung (in German). Archived from the original on July 3, 2019. Retrieved February 21, 2020.