An outline of your themes essentially serves as the outline for your literature review. Establishing the structure of your outline enables you to develop a line of reasoning that justifies your research problem. Your themes may have sub-themes or sub-topics, which serve to break your high-level themes in more comprehensible and discrete ideas. There are various ways to outline or organize your literature review—it will depend on how you group the themes. You may want to also consider using a graphic organizer or concept map to help you map out and determine a structure of your themes.