1. A variational principle and an energy theorem for small-amplitude disturbances of electron beams and of electron-ion plasmas
2. E. M. Barston, “Electrostatic Oscillations of Cold Inhomogeneous Plasmas,” Microwave Laboratory Report, Stanford University (to be published).
3. The set of parameters λ, μ, ⋯ should include as a subset three parameters α, β, γ, which occur in ξT, ζT, and φT respectively as simple multipliers, e.g., ξ0, ζ0 and φ0 in Eq. (33). Such parameters are both desirable and appropriate because our Lagrangian density is a homogeneous function of the second degree in its variables (and therefore, admits of linear Euler-Lagrange equations) and these variables may all be considered to vanish at the boundary of the region of integration.
4. Persistence of Stability in Lagrangian Systems