When you directly quote, paraphrase, or reference another source that has influenced your own work, you need to provide a proper citation. You should also provide documentation for any statistics or facts that are not considered common knowledge.
Citation is necessary to:
Proper citation formats are determined by the particular citation style guide that you are following. Usually your professor will include the required or preferred citation style in your assignment instructions. If you're not sure what style you should use, ask your professor for clarification.
This guide includes examples to help with citation formats in the most commonly used styles: