1. Staffofthe Ramo-Wooldrige ResearchLaboratoryElectrostaticPropulsion.ProceedingsoftheIRE,Vol.48, No. 4, 1960.
2. Wells, W.H. The Neutralization Problem of Electric Propulsion. JPL TR 34-118, Pasadena CA, October 1960.
3. Progress in Astronautics and Rocketry;Watson W.K.R.,1961
4. Progress in Astronautics and Rocketry;French P.,1961