The Treaty of Versailles in the mind of the Germans stabbed them in the back, especially the guilt clause that made them take blame for the First World War. Hitler capaitalized on these sentiments and used them to rally the German people.
Secondary Sources are materials that digest, analyze, evaluate and interpret information contained within primary sources or other secondary sources. Examples. 1  Autobiographies, memoirs, diaries, emails, oral histories.  Letters, correspondences, eyewitnesses.
In some academic disciplines the distinction between a secondary and tertiary source is relative, but in historiography it is absolute. In the UNISIST model, a secondary source is a bibliography, whereas a tertiary source is a synthesis of primary sources.