专家：我国雾霾高发可能还将持续一二十年 (Expert: extensive smog may continue in China for 10 to 20 years)
China National Radio , December 10, 2013
http://china.cnr.cn/yxw/201312/t20131210_514366764.shtml
Guangdong may withhold free permits in China's 4th emissions scheme: sources
Reuters, December 12, 2013
www.reuters.com/article/2013/12/12/china-guangdong-carbon-idUSL3N0JR0C220131212