As easy to search as Google, but focuses on scholarly books, articles, documents
Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Use Google Scholar to find articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles available across the web. Once you set your institutional preferences, links to full-text, if available at Penn State, should appear.
How do I know if a web site is credible enough to use in my paper?
Who is supplying the information?
Is it an educational institution (.edu extension)? A government agency (.gov)? A commercial supplier (.com)? A non-profit organization (.org)?
Is the supplier a reputable organization? (look for an “About Us” link on the homepage)
Is there an author or contact person named? What are the author's credentials?
Has this site been reviewed by experts or professional organizations?