All great essays are built on sources written by experts. Some argue that in most cases around 75% of your essay should be cited. It is essential that every body paragraph answers your research question with evidence. All of that evidence should be cited. Without proper citations, you are in danger of plagiarizing, whether it is intentional or not. Plagiarism on an Extended Essay results in a failing grade. When in doubt, check with your Supervisor or EE Coordinator.