重污染天何时启动预警机制 沪环保部:需三个条件 (Authorities explain why Shanghai’s pollution early warning system not triggered even at AQI 237)
Eastday.com, November 7, 2013
http://sh.eastday.com/m/20131107/u1a7760537.html
北京今天起开始点火试供暖 引发雾霾加剧担忧 (Beijing heating service starts today raising concern about worsening smog)
China News Service, November 7, 2013
http://news.sina.com.cn/c/2013-11-07/165128648799.shtml