Reuters | Global shares up at end of down week, oil prices retreat Reuters Brent oil fell below $50 a barrel after Thursday's spike on Saudi-led air attacks in Yemen, and the dollar was down. Investors awaited a speech on monetary policy on Friday by Federal Reserve Chair Janet Yellen that may contain hints on when U.S ... Yellen in SF, oil trade gets messy & biotechs hit a bump: What to watch Global shares advance at end of down week, oil prices retreat |