It comes amid similar attempts in London by the City's regulator, the Financial Services authority, to "talk tough" about short-sellers manipulating shares in banking stocks. among the firms that have received subpoenas from the SEC, led by chairman Christopher Cox, are Citadel Investment Group in Chicago and SaC Capital advisers in Stamford, Connecticut. The subpoenas relate to trading in securities of the brokers, as well as correspondence between the hedge funds and other parties, according to people familiar with the inquiry.