1. Prescott, J. R., Hough, J. H., and Pidcock, J. K., Proc. Eleventh IUPAP Conf. on Cosmic Rays, Budapest, Acta Physica Hungarica, 29, Suppl. 3, 717 (1970).
2. Allan, H. R., Clay, R. W., and Jones, J. K., Nature, 224, 253 (1970).
3. Stubbs, T. J., Nature Physical Science, 230, 172 (1971).
4. Jasik, H., (ed.), Antenna Engineering Handbook (McGraw-Hill, New York, 1961); Hansen, R. C. (ed.), Microwave Scanning Antennas, 2 (Academic Press, New York, 1966).
5. Hough, J. H., and Prescott, J. R., Nature, 227, 590 (1970).