  In the application of potential models, the use of the Dirac equation in
central potentials remains of phenomenological interest. The associated set of
decoupled second-order ordinary differential equations is here studied by
exploiting the phase-integral technique, following the work of Froman and
  Froman that provides a powerful tool in ordinary quantum mechanics. For
various choices of the scalar and vector parts of the potential, the
phase-integral formulae are derived and discussed, jointly with formulae for
the evaluation of Stokes and anti-Stokes lines. A criterion for choosing the
base function in the phase-integral method is also obtained, and tested
numerically. The case of scalar confinement is then found to be more tractable.
