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2. An infra-red reflectometer with spheroidal mirror;Blevin;J. Sci. Instrum.,1965
3. Current developments in pyrheliometric techniques;Drummond;Solar Energy,1961
4. IGY Instruction Manual Part VI. Pergamon Press, New York, 378-380.
5. Kohlrausch, F. Lehrbuch der praktischen Physik. Teubner, Leipzig, 10th Ed., 41.