CORRECTS DAY OF WEEK - A woman wearing a mask for protection against air pollution walks on a pedestrian overhead bridge in Beijing as the capital of China is shrouded by heavy smog on Tuesday, Dec. 20, 2016. Thick, gray smog fell over Beijing on Tuesday, clouding China's capital in a haze that spurred authorities to cancel flights and close some highways in emergency measures to cut down on air pollution. (AP Photo/Andy Wong)
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