http://ru.wikipedia.org/wiki/%D0%90%D0%BB%D1%8C%D0%BF%D0%B8%D0%B9%D1%81%D0%BA%D0%B0%D1%8F_%D1%80%D0%B0%D1%81%D0%B0http://ru.wikipedia.org/wiki/%D0%9F%D0%BE%D0%BD%D1%82%D0%B8%D0%B9%D1%81%D0%BA%D0%B0%D1%8F_%D1%80%D0%B0%D1%81%D0%B0http://sknowledge.ru/Msg.aspx?id=8600