MADRID, Aug 21 (Reuters) - Spain announced the following results at Tuesday's Treasury bill auction . (Amounts bid, allocated in millions of euros) ISSUE YIELD PREVIOUS PRICE PREVIOUS BID ALLOCATED 3-month -0.521 -0.470 100.122 100.110 1,750.12 325 9-month -0.434 -0.387 100.314 100.280 4,020.00 1,430 The bid-to-cover ratio on the 3-month bill was 5.38 versus 3.4 at the last auction. The bid-to-cover ratio on the 9-month bill was 2.81 versus 3.4 at the last auction. For further information, click on and . (Reporting by Madrid Newsroom)