It is imperative that you acknowledge any sources you use in your written and creative work. You can do this by selecting a documentation style and using it consistently to cite your sources. Documentation styles include MLA, APA, Chicago, and others. Your area of study generally determines which style to use and your instructors will generally let you know which style they want you to use. If you are using copyrighted materials for commercial purposes you must obtain permission from the copyright holder and post permission granted notices, as necessary, in your work.