OneSearch is - in part - the UNI Library catalog. OneSearch can be used to find both older books (primary sources) and newer secondary source books written by historians. OneSearch connects you to roughly on million print books and hundreds of thousands of ebooks.
JSTOR - provides secondary history sources if limited to "History" and publication date after 1985
JSTOR can be used to find secondary sources written by historians by setting the publication date from 1985 to the present - and by selecting the "History" discipline located towards the bottom of the page.
America History & Life - Indexes Secondary Sources written by historians.
Searches the title and subject of over 200,000 books. To search the entire text of these books change the dropdown menu to "TX All Text Fields" to search the full text of each book. eBook Collection provides access to secondary sources written by historians.