A non-perturbative approach to the bound polaron. III
S. Mukhopadhyay, Tapas Mitra · Journal of Physics C Solid State Physics · 1981
For pt.II see ibid., vol.13, p.3193 (1980). The formal difficulties of the non-perturbative iteration variational method proposed recently for the ground state of the bound polaron problem are removed by a rigorous method of canonical transformation which not only yields essentially equivalent results but also extends its validity to excited states.