As you search in the online catalog, watch for the words "personal narratives," "diaries," "interviews," "correspondence," "pamphlets," and "sources" as part of the subject headings; these may point you to published primary sources in the library collections.
You can also search for these words, for example, paris and occupation and (diaries or narratives or correspondence or sources or pamphlets or interviews)
Other clues may be buried in the title, authorship, date of publication, etc.
Books are an excellent source for images, containing images reproduced from archives and collections that might be difficult to access. Books of images will often include essays, memoirs, and other descriptive text to help contextualize the images (unlike Google Images).
Try these Subject Begins With searches in the online catalog: