1. I. Langmuir,The Collected Works of Irving Langmuir, edited by C. Suits (Pergamon Press, Inc., New York, 1961), Vol. 4, pp. 23–132.
2. D. Bohm, inCharacteristics of Electrical Discharges in Magnetic Fields, edited by A. Guthrie and R. Wakerling (McGraw-Hill Book Company, Inc., New York, 1949), Chap. 3.
3. Theory of Electrostatic Probes in a Low-Density Plasma
4. Continuum Theory of Spherical Electrostatic Probes