An outline, also called a hierarchical outline, is a list arranged to show hierarchical relationships and is a type of tree structure. It is used to present the main points or topics of a given subject, often used as a rough draft or summary of the content of a document. Preparation of an outline is an intermediate step in the process of writing a scholarly research paper, literature review, thesis or dissertation. A special kind of outline (integrated outline) incorporates scholarly sources into the outline before the writing begins.