1. Qi-wen Jin, Hai-zhen Yu. China's national conditions and strength, Vol. 10 (2009), p.32 (In Chinese).
2. Yu Lei, Qiang Zhang, et al. 1990-2020. Atmospheric Environment. Vol. 45 (2011), p.147 (In Chinese).
3. Yu-tao Wang. China Equipment Engineering, Vol. 7(2009), p.69 (In Chinese).
4. Jiong-qiong Hu; Ke-she Jiang n; Yu-liang Cai. Ecological Economy, Vol. 5, (2007), p.181.
5. Jian-ping Zhu, et al. Ceramic Society , Vol. 2(2003), p.57 (In Chinese).