Victor Klemperer was a Romance languages scholar, who also became known as a diarist, whose journals, published in Germany in 1995, detailed his life under the German Empire, the Weimar Republic, Nazi Germany and the German Democratic Republic. His journals covering the period of the Third Reich have since become standard sources, and have been extensively quoted by Saul Friedländer, Michael Burleigh, Richard J. Evans and Max Hastings.

https://en.wikipedia.org/wiki/Victor_Klemperer