Order Granting Approval of a Proposed Rule Change, as Modified by Amendment No. 1, Relating to Proposed Rule G-43, on Broker's Brokers; Proposed Amendments to Rule G-8, on Books and Records, Rule G-9, on Record Retention, and Rule G-18, on Execution of Transactions; and a Proposed Interpretive Notice on the Duties of Dealers That Use the Services of Broker's Brokers