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2. Personal communication with Paul Freund of the IEA Greenhouse Gas R&D Programme.
3. IEA World Energy Outlook (2000 data).
4. M. Simmonds, P. Hurst, M.B. Wilkinson, C. Watt, C.A. Roberts, in: Proceedings of GHGT-6, vol. 1, Kyoto, Japan, 2003, pp. 39–44.
5. K. Nissen, in: Proceedings of Ecos2003, vol. 1, Copenhagen, Denmark, 2003, pp. 109–116.