1. Hundhausen, A. J.: 1979,Rev. Geophys. Space Phys. 17, 2032.
2. Iucci, N., Parisi, M., Storini, M., and Villoresi, G.: 1979,Nuovo Cimento 2c, 421.
3. King, J.: 1983,Interplanetary Medium Data Book - Supplement 2, 1978?1982, NSSCD/WDC-A, Goddard Space Flight Centre, Greenbelt, MA.
4. King, J.: 1986a,Interplanetary Medium Data Book - Supplement 3, NSSD/WDC-A, Goddard Space Flight Centre, Greenbelt, MA.
5. King, J.: 1986b,Interplanetary Medium Data Book - Supplement 3A, 1977?1985, NSSCD/WDC-A, Goddard Space Flight Centre Greenbelt, MA.