  As opposed to Arminjon statements, in this work we again assert the absence
of the non-uniqueness problem of the Dirac theory in a curved and flat
spacetime and illustrate this with a number of examples. Dirac Hamiltonians in
arbitrary, including time-dependent, gravitational fields uniquely determine
physical characteristics of quantum-mechanical systems irrespective of the
choice of the tetrad fields. Direct spin-rotation coupling that occurs with a
certain choice of tetrads does not manifest itself in final physical
characteristics of the systems and therefore does not represent a physically
relevant effect.
