While not official subject headings, these keywords can be very fruitful for your research. Keyword searches look at all the information in the book or article record including title, author, abstract, table of contents, etc.
Examples:
Immigration
Workers Rights
Labor Issues
Racism and Social Justice
American Dream
Using the correct words to search will help you find relevant information. Different authors and search tools use different words to describe the same concepts, so it is useful to have a list of similar and related terms in your arsenal when you set out to search for relevant information. The process of creating these alternative terms is called brainstorming terms or concept mapping.
Example:
American Dream and Discrimination
Immigrants and Migrant Workers
Immigrants and Bracero Program
Poverty and Children
American Dream and immigrants
Dream Act and immigrants
Poverty and Race
Migrant workers and Rights and Domestics