A Free-Field Lagrangian for a Gauge Theory of the CPT Symmetry
  A simplified mathematical approach is presented and used to find a suitable
free-field Lagrangian to complete previous work on constructing a gauge theory
of CPT transformations. The new Lagrangian is a slight but important
modification of the previous candidate. The new version satisfies an additional
requirement which had been overlooked and not satisfied by the previous
candidate.
