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2. ASHRAE, Applications Handbook (SI). American Society of Heating, Refrigerating and Air Conditioning Engineers, Atlanta, GA, U.S.A., 1995.
3. The Influence of Height Above Sea Level on the COP of Air-Source Heat Pumps Used for Water Heating
4. Weather Bureau, Climate of South Africa, Climate Statistics up to 1984, WB40. Government Printer, Pretoria, South Africa, 1988.