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.
Primary sources are the first hand evidence left behind by participants or observers at the time of events. Primary sources originate in the time period that historians are studying. They vary a great deal.
Other types of primary sources are paintings created by the artist. If it were a photocopy of the painting, then it would be a secondary source. Some other primary sources are letters, films, short stories, plays, poems, photographs, court cases, journal articles, newspaper events, and speeches. For instance, a speech by President Bush would be a primary source.