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. 2016 Dec 9;6(12):e013376. doi: 10.1136/bmjopen-2016-013376

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Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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Location of Chaoyang city. Chaoyang is located in the northwest part of Liaoning province, and the climate is a typical northern temperate continental monsoon climate.