https://www.gauss-friends.org/ar/2019/04/30/de-gauss-telegraph-buchvorstellung-c-f-gauss-und-johanna-begegnungen-der-besonderen-art-en-gauss-telegraph-book-release-c-f-gauss-and-johanna-encounters-of-a-special-kind/
(English) Gauss-Telegraph: Book release "C.F. Gauss and Johanna - Encounters of a special kind"