Special libraries often have a more specific clientele than libraries in traditional educational or public settings, and deal with more specialized kinds of information. They are developed to support the mission of their sponsoring organization and their collections and services are more targeted and specific to the needs of their clientele. Special libraries may or may not be open to the general public. Those that are open to the public may offer services similar to research, reference, public, academic, or children's libraries, often with restrictions such as only lending books to patients at a hospital or restricting the public from parts of a military collection. Many special libraries are not open to the general public, though access may be requested for specialized research by request. Special libraries are also sometimes known as "information centers." Some authors differentiate special libraries from information centers by defining the latter as having "a very narrow scope." They are generally staffed by librarians, although many librarians employed in special libraries are specialists in the library's field rather than generally trained librarians, and often are not required to have advanced degrees in specifically library-related field due to the specialized content and clientele of the library. However, it is not uncommon for librarians at special libraries to have both a library science degree as well as a degree or experience of some type in the field their library specializes in as opposed to either only library science or field specific experience.