Salmon, Lynn G.; Christoforou, Christos S.; Cass, Glen R. (1994). “Airborne Pollutants in the Buddhist Cave Temples at the Yungang Grottoes, China”. Environmental Science & Technology (bằng tiếng Anh). 28 (5): 805–811. doi:10.1021/es00054a010. PMID22191820.
megalithic.co.uk
[1]Silk Road, North China, C.Michael Hogan, the Megalithic Portal, ed. A. Burnham, 2007]
nih.gov
pubmed.ncbi.nlm.nih.gov
Salmon, Lynn G.; Christoforou, Christos S.; Cass, Glen R. (1994). “Airborne Pollutants in the Buddhist Cave Temples at the Yungang Grottoes, China”. Environmental Science & Technology (bằng tiếng Anh). 28 (5): 805–811. doi:10.1021/es00054a010. PMID22191820.