1. Shorthill, R. W., and Saari, J. M., Boeing Res. Lab. Rep., D1–82–0404 (1965).
2. Murray, B. C., Rep. Roy. Soc. Disc., London (June, 1965).
3. Gear, A. E., and Bastin, J. A., Nature, 196, 1305 (1962).
4. Shorthill, R. W., Boeing Res. Lab. Rep., D1–82–0196 (1962).
5. Pettingill, G. H., and Henry, J. C., J. Geophys. Res., 67, 4881 (1962).