Читаем википедию, опять же: http://ru.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B5%D1%87%D0%B5%D0%BD%D1%8C_%D0%B0%D1%82%D0%BE%D0%BC%D0%BD%D1%8B%D1%85_%D1%80%D0%B5%D0%B0%D0%BA%D1%82%D0%BE%D1%80%D0%BE%D0%B2,_%D1%81%D0%BF%D1%80%D0%BE%D0%B5%D0%BA%D1%82%D0%B8%D1%80%D0%BE%D0%B2%D0%B0%D0%BD%D0%BD%D1%8B%D1%85_%D0%B8_%D0%BF%D0%BE%D1%81%D1%82%D1%80%D0%BE%D0%B5%D0%BD%D0%BD%D1%8B%D1%85_%D0%B2_%D0%A1%D0%BE%D0%B2%D0%B5%D1%82%D1%81%D0%BA%D0%BE%D0%BC_%D0%A1%D0%BE%D1%8E%D0%B7%D0%B5