text: The Dow Jones industrial average slipped 5.23 points to 16,995.13.
  The S&P 500 gained 0.31 points to 1,989.57, while the tech-focused Nasdaq index fell 12.22 points to 4,662.16.
  US markets mirrored those in Europe after ECB head Mario Draghi said the bank would expand stimulus measures, but did not expect further rate cuts.
  Shares in mobile payment company Square fell 6.1%. The company reported on Wednesday that it had seen growth in payment volume over the fourth quarter, but also increasing operating expenses.
  Dollar General shares rose 10.7% after the company reported profits of $376m. Its discount competitor Dollar Tree saw its share price rise 4%.
target: (Close): US stocks finished mostly lower following a turbulent trading day and an announcement of new stimulus from the European Central Bank.