From Harvard's Kennedy School of Government library, this link is a custom Google search + list of hundreds of US and international think tanks affiliated with universities, governments, advocacy groups, foundations, non-governmental organizations, and businesses that generate public policy research, analysis, and activity.
HeinOnline Academic includes more than 100 million pages of multidisciplinary content in more than 100 subject areas, including history, political science, criminal justice, religious studies, international relations, women’s studies, pre-law, and many more. HeinOnline provides access to 300+ years of information on political development and the complete history of the creation of government and legal systems around the world.
Statista.com provides companies, business customers, research institutions, and the academic community with direct access to quantitative data on media, business, finance, politics, and a wide variety of other areas of interest or markets.
Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research.
Find popular sources
Popular sources are written by the general public. They include sources like newspapers. They can be useful for exploratory research to help you become aware of the different viewpoints associated with an issue.
Covers a wide range of news, business, legal, medical, and reference information, most available in full text. Includes newspapers, magazines, wire services, federal and state court opinions, federal and state statutes, federal regulations, and SEC filings. Most entries are full-text, some updated daily.