"The purpose of a research paper is to synthesize previous research and scholarship with your ideas on the subject. Therefore, you should feel free to use other persons' words, facts, and thoughts in your research paper, but the material you borrow must not be presented as if it were your own creation." (MLA Handbook for Writers of Research Papers, 7th ed., p.55)
There are many different writing styles and ways of citing sources. The style usually depends on the academic discipline involved. to make sure you use the required style. Whatever style you use, BE CONSISTENT.