1. P. T. Anastas and J. C.Warner , Green Chemistry: Theory and Practice , Oxford University Press , Oxford , 1998
2. M. Lima , The Book of Trees. Visualizing Branches of Knowledge , Princeton Architectual Press , New York , 2014
3. The Raleigh Register, Coal Products Tree, http://williamsonlibrary.lib.wv.us/WV20Facts/Coal20mining/coaltree.htm
4. Dept. of the Environment (Australia) , Estimate of the cost of hazardous waste in Australia , Canberra, ACT , 2014
5. United Nations Environment Programme (UNEP)