Lord Rayleigh published a generalization of the virial theorem in 1900 which was partially reprinted in 1903. Henri Poincaré proved and applied a form of the virial theorem in 1911 to the problem of formation of the Solar System from a proto-stellar cloud (then known as cosmogony). A variational form of the virial theorem was developed in 1945 by Ledoux. A tensor form of the virial theorem was developed by Parker, Chandrasekhar and Fermi. The following generalization of the virial theorem has been established by Pollard in 1964 for the case of the inverse square law: 2 lim τ τ → → + ∞ ∞ ⟨ ⟨ T ⟩ ⟩ τ τ = lim τ τ → → + ∞ ∞ ⟨ ⟨ U ⟩ ⟩ τ τ if and only if lim τ τ → → + ∞ ∞ τ τ − − 2 I ( τ τ ) = 0 . A boundary term otherwise must be added.