1. Cocke, W. J., Disney, M. J., and Taylor, D. J., Nature, 221, 525 (1969).
2. Fritz, G., Henry, R. C., Meekins, J. F., Chubb, T. A., and Friedman, H., IAU Circ. No. 2141 (1969);
3. Fritz, G., Henry, R. C., Meekins, J. F., Chubb, T. A., and Friedman, H., IAU Circ. No. 2141 (1969); Science (in the press).
4. Gorenstein, P., Kellogg, E. M., and Gursky, H., Astrophys. J., 156, 315 (1969).
5. Oke, J. B., Astrophys. J. Lett., 156, L49 (1969).