All digital resources listed here are by SMU subscription (login required from off-campus).
You will usually be expected to find scholarly articles in academic journals -- specifically, in what are called "refereed" (or "peer reviewed") journals. This means that the articles have been reviewed ("refereed") by experts in the field, and that these experts have judged the articles to be worthy of publication.
In a database such as Historical Abstracts, most of the results you get will be peer-reviewed articles. However, you can be certain of whether or not you are finding refereed articles by selecting "Peer Review" from the list of search refinements that is available on the left sidebar of every results page.
Any topic regarding U.S. or Canadian history
Any topic relating to religion
Books: Balance basic keyword searches in the library catalog with advanced searches that permit searching by the "subject headings"
Books can be secondary or primary resources.
Search these resources for books
Near comprehensive list of books from libraries worldwide, includes links to request materials through ILL