These databases contain scholarly (peer-reviewed) and popular articles, reports, and grey literature from publication in the legal and political science disciplines. Since they are discipline-specific, there is often a lot of authoritative and well cited information on the topic. However, the peer-review process takes time. You also need to be mindful of what type of source you have retrieved - policy papers, reports, and grey literature should be evaluated carefully.
Sometimes topics we are discussing are not contained to one specific discipline. In this case you will want to use a database that contains articles from the sciences, social sciences, and arts & humanities. They are a great way to see who is talking about your topic and to expand your research.
While most books are not considered scholarly sources, you can find collections of peer-reviewed articles that are collected into an edited book on a particular topic. The best place to search for these books is the ProQuest E-Book Central, but you may want to also try the Library's catalog, WorldCat.
A think tank is a not-for-profit research institution, usually separate from a university, that conducts applied, policy-relevant research and analysis; and is involved in public affairs as well. When using think tanks, you need to be mindful that think tanks can be, and often are, advocacy oriented. The fact that a think tank refers to itself as non-partisan just means that it has no formal connection to a political party, not that it doesn’t have an ideological orientation that may be more consistent with a given political party..
These are just some of the dozens of Think Tanks in the U.S. and worldwide. Search Google for your topic + think tank for more.
A non-governmental organization (NGO) is an organization that is neither a part of a government nor a conventional for-profit business. Usually set up by ordinary citizens, NGOs may be funded by governments, foundations, businesses, or private persons. Some avoid formal funding altogether and are run primarily by volunteers.
An Intergovernmental Organization (IGO) is a coalition of foreign governments which work together to promote common ends. That can be humanitarian, political, economic, educational or social good. The biggest and oldest example is the United Nations. There are many dozens of these organizations now; several of the largest began within the UN but are now semi-autonomous (such as the World Bank, World Health Organization; and the International Monetary Fund).
Popular sources, like Newspapers and Magazines are intended for a general audience of readers and are written typically to entertain, inform, or persuade. Popular sources help you answer who, what, when, and where questions and are essential for finding information about current events or issues. They are typically the fastest way to get information after an events has occured.
Government documents and publications offer a wealth of information on hundreds of topics in addition to their primary role of recording the work of countries and states.