This paper deals with a class of nonlinear Dirac equations. We relate their solutions to those of nonlinear Schrödinger equation by a perturbation parameter. It is demonstrated that the nondegenerate solution (ground state) of Schrödinger equation generates solutions for Dirac equation.
"Perturbation method for a class of nonlinear Dirac equations." Differential Integral Equations 13 (4-6) 707 - 720, 2000.