Of the 19,500 Jewish citizens of Cologne in 1930, about 11,000 were killed during by Nazi regime.Kirsten Serup-Bilfeld, Zwischen Dom und Davidstern. Jüdisches Leben in Köln von den Anfängen bis heute. Köln 2001, p. 193 Some of them were killed after they left Germany to avoid Nazi persecution. Among others, the Cologne lawyer Siegmund Klein and his son Walter Klein were killed in Auschwitz concentration camp, after being deported respectively from the Netherlands and France in 1943 and 1942.Giorgio Sacerdoti, Falls wir uns nicht wiedesehen..., Prospero Verlag, Münster 2010
