Historical index with citations from 375 popular magazines published in the U.S. & Canada from 1890-1920, covering subjects such as current events, business, politics, education, history, sports & science.
The Internet Archive, a 501(c)(3) non-profit, is building a digital library of Internet sites and other cultural artifacts in digital form.
Thishandout by Prince George's Community College is a visual representation of how boolean operators work and how they can help narrow or broaden your results.
Using Different Type of Keywords
When brainstorming more keywords try thinking of different types of keywords: narrower (for specific results), broader (general results), similar (synonyms), and related (information about related topics).