The Online Writing Lab at Purdue Many instructors refer to the free OWL web-site because it provides accurate and informative resources on writing and citation issues.
As a college student you are expected to cite those sources which you quote, paraphrase or otherwise use in preparing your papers, reports and presentations.
The three most frequently used citation styles for students are APA (American Psychological Association), MLA (Modern Language Association) Chicago Style (University of Chicago); see the ASU Library: Citation Style for more information.
Cited sources assist your professors in determining how thorough you were in identifying supporting evidence
Cited sources demonstrate your awareness of the range of literature on a topic.
Cited sources provide your reader with the information necessary for retrieving a copy of the item in case she wishes to consult it herself.
And yes, citing of sources is an ethical practice required by the university's Academic Integrity policy.