http://ru.wikipedia.org/wiki/%D0%A1%D0%BE%D1%86%D0%B8%D0%B0%D0%BB%D1%8C%D0%BD%D0%BE-%D0%BE%D1%80%D0%B8%D0%B5%D0%BD%D1%82%D0%B8%D1%80%D0%BE%D0%B2%D0%B0%D0%BD%D0%BD%D0%B0%D1%8F_%D1%80%D1%8B%D0%BD%D0%BE%D1%87%D0%BD%D0%B0%D1%8F_%D1%8D%D0%BA%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D0%BA%D0%B0Ознакомьтесь для общего развития