More about the $j=0$ relativistic oscillator
  I start from the Bargmann-Wigner equations and introduce an interaction in the form which is similar to a $j=1/2$ case [M. Moshinsky & A. Szczepaniak, {\it J. Phys. A}{\bf 22} (1989) L817]. By means of the expansion of the wave function in the complete set of $\gamma$- matrices one can obtain the equations for a system which could be named as the $j=0$ Kemmer-Dirac oscillator.   The equations for the components $\phi_1$ and $\phi_2$ are different from the ones obtained by Y. Nedjadi & R. Barrett for the $j=0$ Duffin-Kemmer-Petiau oscillator [{\it J. Phys. A} {\bf 27} (1994) 4301]. This fact leads to the dissimilar energy spectrum of the $j=0$ relativistic oscillator. 
Valeri V. Dvoeglazov