1. X. Huang and B. W. Reinisch, Vertical electron density profiles from the Digisonde network, this issue.
2. Observations of the mid-latitude F1 region;McNamara;Adv. Space Res.,1995
3. A method of predicting the F1 layer critical frequency;Ducharme;Radio Sci.,1971
4. The Digisonde network and databasing;Reinisch;World Data Center A for Solar-Terrestrial Physics, Report UAG-104,1995
5. D. N. Anderson, A. J. Trebble and D. T. Decker, Improving IRI 90 low latitude ionospheric specifications, this issue.