1. An effective ground conductivity map for continental United States;Fine,1954
2. Nature of lightning discharges as origins of atmospherics;Ishikawa,1961
3. Ground conductivity determinations at low radio frequencies by an analysis of the sferic signatures of thunderstorms;Johler;J. Geophys. Res.,1961
4. Effective radio ground conductivity measurements in the United States;Kirby,1954
5. A comparison of intracloud and cloud to ground lightning discharge;Kitagawa;J. Geophys. Res.,1960