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Encyclopedias give general background information and can help you to define terms and get a brief overview. They also have lots of references, providing a good starting point for the primary literature.
You can find other encyclopedias or scientific dictionaries in your area by searching in Franklin or FindIt! or by browsing the TP call number ranges in the Chemistry and Engineering Libraries' print reference collections.
Print reports since 1993 may be found on the third floor of Van Pelt Library at call number TP155 .C5465. The link above provides a listing of available reports in Franklin, Penn Libraries online catalog.
Books are a great source of background information on a topic. They are more specific than encyclopedias, but they're still general enough to be understandable early in the research process. One thing to be aware of with this type of literature, however, is that the information contained is not terribly up-to-date, as the publication process for a book is lengthy.
You can find a lot of relevant books by browsing the TP call number sections of the Chemistry and Van Pelt Libraries collections, or you can try searching the following e-resources.