может здесь что-нибудь за основу взятьhttp://books.google.pt/books?id=v0LpAgAAQBAJ&pg=PA528&lpg=PA528&dq=%D0%B7%D0%B0%D0%B3%D0%B0%D0%B4%D0%BA%D0%B0+%D0%BF%D1%80%D0%BE+%D0%B3%D0%BE%D0%BB%D0%BE%D0%B4&source=bl&ots=JO-H6qC8dS&sig=3hW3KsDBeYx6uNrCXoWiNqt2iT8&hl=ru&sa=X&ei=fLs_VKr4ENHiaq-ggKAB&ved=0CB4Q6AEwADgU#v=onepage&q=%D0%B7%D0%B0%D0%B3%D0%B0%D0%B4%D0%BA%D0%B0%20%D0%BF%D1%80%D0%BE%20%D0%B3%D0%BE%D0%BB%D0%BE%D0%B4&f=false