1. Riihimaa, J. J., Astron. J. (in the press).
2. Riihimaa, J. J., Astrophys. Lett. (in the press).
3. Gordon, M. A., and Warwick, J. W., Astrophys. J., 148, 511 (1967).
4. Riihimaa, J. J., Nature, 212, 1338 (1966).
5. Brown, G. W., Carr, T. D., and Block, W. F., Astrophys. Lett., 1, 89 (1968).