In a research paper, you will draw on the work of other researchers and writers, and you must document their contributions by citing your sources. Sources are cited for two reasons:
You must cite anything you borrow from a source, including direct quotations; statistics and other specific facts; visuals such as tables, graphs, and diagrams; and any ideas you present in a summary or paraphrase. Borrowing without proper acknowledgment is a form of dishonesty known as plagiarism.
The only exception is common knowledge—information that your readers may know or could easily locate in any number of reference sources.