  Vector couplings in the Duffin-Kemmer-Petiau theory are revised. It is shown
that minimal and nonminimal vector potentials behave differently under
charge-conjugation and time-reversal transformations. In particular, it is
shown that nonminimal vector potentials have been erroneously applied to the
description of elastic meson-nucleus scatterings and that the space component
of the nonminimal vector potential plays a crucial role for the confinement of
bosons. The DKP equation with nonminimal vector linear potentials is mapped
into the nonrelativistic harmonic oscillator problem and the behavior of the
solutions for this sort of DKP oscillator is discussed in detail. Furthermore,
the absence of Klein's paradox and the localization of bosons in the presence
of nonminimal vector interactions are discussed.
