The main search tools for finding books, articles, databases, archival collections, and more at Yale (and beyond) can all be found on the "Find, Request, and Use" page of the library's website. Here are a few quick refreshers, but be sure to visit the page for a full overview:

Background or "reference" sources are a great place to start your research. Reference works include bibliographies, scholarly encyclopedias, dictionaries, handbooks, and other sources that provide overviews of topics and suggestions for further reading.

Praeger Security International: Terrorism, Homeland Security, Strategy

Provides information on international security relevant to contemporary issues in the 21st century. Treats topics such as arms control, defense and national security, energy security, cyber conflict, counterinsurgency, and terrorism. Offers perspectives from psychologists, diplomats, first responders, economists, journalists, civil servants, war-fighters, and legal experts.

Gale in Context: U.S. History

This resource brings together reference articles, along with selected primary and secondary sources for getting started on your research.

Oxford Bibliographies

This is an extensive collection of annotated bibliographies that are keyword searchable and can also be browsed by subject area --

e.g., Political Science

Oxford Handbooks Online
Lengthy chapters in the Oxford Handbooks usually provide helpful overviews of scholarly topics and historical literature, along with suggestions for further reading. A number of the handbooks may be helpful depending on your research topic.

Oxford Research Encyclopedia of American History 
A scholarly encyclopedia of potentially great use in the early stages of your research project. Each article has a discussion of the literature, including primary sources -- often a great starting point for finding more sources.

Oxford Research Encyclopedia of Politics

Cambridge Core

Link to the general collections of Cambridge University Press, including the Cambridge Histories and Cambridge Companions.

Wiley Online Library

Includes scholarly journal articles and monographs as well as reference works. Often a single chapter or two within a reference work can provide a helpful starting point for research. The Wiley Companions will be especially useful. Navigate to "Humanities" and then "History" to find a detailed listing of titles by subfield.

The following bibliographic databases will be helpful for finding secondary sources, especially scholarly/peer-reviewed journal articles, magazine articles, book reviews, and citations to book chapters and edited collections of books. Please note: the full text of articles will not always be available in these databases. If you see the "YaleLinks" icon instead of a PDF, click on the icon to discover whether we have online access to the article: 

And, don’t forget, Orbis, Books+ and Articles+ are all useful tools for locating secondary sources!