An abstract is a brief summary of a research article, thesis, review, conference proceeing or any in-depth analysis of a particular subject or discipline, and is often used to help the reader quickly ascertain the paper's purpose. When used, an abstract always appears at the beginning of a manuscript, acting as the point-of-entry for any given scientific paper or patent application. Abstraction and indexing services are available for a number of academic disciplines, aimed at compiling a body of literature for that particular subject.