1. Hirman, J., Losey, R., and Heckman, G.: 1975, ?A Compilation of Solar Flares Reported during the Skylab Mission-Preliminary Copy?.
2. Martin, S. F. and Ramsey, H. E.: 1972, in P. S. McIntosh and M. Dryer (eds.) Solar Activity Observations and Predictions, MIT Press, Cambridge.
3. Pallavicini, R., Vaiana, G. S., Kahler, S. W., and Krieger, A. S.: 1975, Solar Phys. 45, 411.
4. Vaiana, G. S., Krieger, A. S., Petrasso, R., Silk, J. K., and Timothy, A. F.; 1974, Proc. Soc. Photo-Opt. Inst. Eng. 44, 185.