Use a database or Google Scholar.
A Few Databases To Get Started
- Google Scholar -- covers all subjects. Searches Google Books and also some library databases.
- Academic Search Complete -- A database covering all subjects.
- JSTOR -- A database covering all subjects. Note: Although you don't have access to JSTOR, you can visit a library that does and get access that way. Georgia Gwinnett College, for example, allows visitors. For more information, see here.