To find books on a technological innovation that are primary sources, use the limits on the left side of your results list to limit your search to books published around that time, e.g.
keyword search: telephone and limit to 1870-1890
Search by keyword for Primary Sources in the Main Catalog
You can search the Main Catalog to find direct references to primary source material. Perform a keyword search for your topic and add one of the words below:
(these are several examples of words that would identify a source as primary)
* early works
* personal narratives
Google Books and Hathitrust have similar content and usage. Full text of materials published in the United States before 1923 are available in both of these resources. The full text for books after 1923 can not be accessed online because of copyright restrictions, but the search is still useful for two purposes:
If you find a book you want, check the Princeton catalog to see if Princeton owns it.