Upon requisition of the Secretary of the Senate and the Clerk of the House of Representatives, respectively, the Director of the Government Publishing Office shall furnish stationery, blank books, tables, forms, and other necessary papers preparatory to congressional legislation, required for the official use of the Senate and the House of Representatives, or their committees and officers. This does not prevent the purchase by the officers of the Senate and House of Representatives of stationery and blank books necessary for sale to Senators and Members in the stationery rooms of the two Houses as provided by law.