US stocks opened higher, helped by a surge in crude oil and Federal Reserve Chair Janet Yellen's comments pointing to resilience in the US economy.
The Dow Jones industrial average was up 64 points, or 0.36%, at 17,605.96, the S&P 500 was up 9.38 points, or 0.46%, at 2,051.29 and the Nasdaq composite was up 35.23 points, or 0.73%, at 4,883.60.