  We show that in a relativistically covariant formulation of the two-body
bound state problem, the bound state spectrum is in agreement, up to
relativistic corrections, with the non-relativistic bound state spectrum. The
solution is achieved by solving the problem with support of the wave function
in an O(2,1) invariant submanifold of the Minkowski spacetime. The O(3,1)
invariance of the differential equation requires, however, that the solutions
provide a representation of O(3,1). Such solutions are obtained by means of the
method of induced representations, providing a basic insight into the subject
of the symmetries of relativistic dynamics.
