1. Montreal protocol on substances that deplete the ozone layer;United Nations Environment Programme (UNEP),1987
2. Kyoto protocol;United Nations Framework Convention on Climate Change (UNFCCC),1997
3. Revival of carbon dioxide as a refrigerant;Lorentzen;Int. J. Refrig,1994
4. Carbon dioxide as the working fluid in heating and/or cooling systems;Fleming;Bull. Int. Inst. Refrig,2003
5. The use of natural refrigerants: a complete solution to the CFC/HCFC predicament;Lorentzen;Int. J. Refrig,1995