1. M. K. Hubbard in ?The Environmental and Ecological Forum 1970?1971?, U.S. Atomic Energy Commission, Office of Information Services, 1972 (N.T.I.S. Document No. TID-25857).
2. M. K. Hubbard,Scientific American,224 (1971) 61.
3. ?Introduction to the Utilization of Solar Energy?, ed. A. M. Zarem and D. D. Erway, McGraw Hill, 1963.
4. ?Direct Energy Conversion?, S. W. Angrist, Allyn and Bacon, 2nd edn, 1971.
5. ?Solar Energy for Man?, B. J. Brinkworth, Compton Press, 1972.