Librarians assist people in finding information and using it effectively for personal purposes. Librarians must have knowledge of a wide variety of public information sources, and follow trends related to publishing, computers, and the media to effectively oversee the selection and organization of library materials. Librarians are classified according to the type of library in which they work—public libraries, school library media centers, academic libraries, and special libraries. Librarians held about 149,000 jobs in 2000.A master's degree in Library Science (MLS) is necessary for librarian positions in most public, academic, and special libraries, and in some school libraries. The Federal Government requires an MLS or the same in education and experience.