1. Low-Frequency Oscillations in a Potassium Plasma
2. Ion Waves in an Inhomogeneous Plasma
3. L. Spitzer, Jr.,Physics of Fully Ionized Gases(Interscience Publishers, Inc., New York, 1962), 2nd ed., p. 24.
4. F. F. Chen, Princeton Plasma Physics Laboratory Report MATT-227 (1963).
5. Reference 3, p. 32.