In a large mixing bowl, mix flour, sugar, cocoa, baking soda and salt. mix well, Make three wells in the flour mixture. In one put vanilla; in another the vinegar, and in the third the oil. Pour the cold water over the mixture and stir until moistened. Pour into 8 x 8-inch pan. Bake at 350°F. oven for 25 to 30 minutes, or until it springs back when touched lightly.