1. Revival of carbon dioxide as refrigerant;Lorentzen;International Journal of Refrigeration,1994
2. J. Pettersen, R. Aarlien, Progress in CO2 Vapour Compression System, in: Proceedings of the Oji International Seminar, Tomakomai City, Hokkaido, Japan, 1997.
3. CO2-heat pump water heater: characteristic, system design and experimental results;Nekså;International Journal of Refrigeration,1998
4. R. Aarlien, P.E. Frivik, Comparison of practical performance between CO2 And R-22 reversible heat pumps for residential use, in: Proceedings of the Natural Working Fluid’98, IIR-Gustav Lorentzen Conference, Oslo, Norway, 1998.
5. G.R. Zakeri, P. Nekså, H. Rekstad, Work Package 11: Prototype System Design and Construction Final Report 01/99, Energy Efficient And Environmental Friendly Heat Pumping Systems Using CO2 As Working Fluid, COHEPS, 1999.