Library of Congress Subject Headings are quite useful for discovering primary sources. The following subheadings usually are added to indicate that the material is a primary source: sources, personal narratives, correspondence, diaries, manuscripts, "early works to 1800" or notebooks. Once you've discovered the subject heading for secondary sources, try adding one of the primary source subheadings to see what you find.

Try searching these subject headings in Primo to find anthologies of primary source materials, available here in Collins Library or via SUMMIT request:

Anti-Nazi movement -- History -- Sources

Germany -- History -- 1933-1945 -- Sources

Germany -- Politics and government -- 1918-1933 -- Sources

Germany -- Politics and government -- 1933-1945 -- Sources

Germany -- Social conditions -- 20th century -- Sources

Germany -- Social conditions -- 1933-1945 -- Sources

Holocaust, Jewish -- 1939-1945 -- Sources

National socialism -- Sources

World War, 1939-1945 -- Personal narratives, German