题目：
Yet in its current dour mood, Europe risks almost overlooking the revolutionary step forward it has taken in creating the world’s largest and wealthiest barrier-free market—and on a continent where, for centuries, economic battles have led to some of history’s bloodiest wars. Moreover, a failure to reinforce the single market by pushing forward with European integration could lead to an unraveling of what the internal market program has achieved, some observers say.
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