вас просветит энциклопедия  http://ru.wikipedia.org/wiki/%D0%A8%D0%B0%D0%BF%D0%BE%D1%87%D0%BA%D0%B0_%D0%B8%D0%B7_%D1%84%D0%BE%D0%BB%D1%8C%D0%B3%D0%B8