“…What intrigued us was the assertion [4] that the 'derivation' leads to the Dirac equation, instead of to the Klein-Gordon equation. To examine this question more closely, we were led to start from the opposite direction to [4], viz., a 'direct' derivation of the Liouville equation through an explicit construction of the Wigner Functions [7] themselves, as in more orthodox approaches [5,6], with a view to throwing some light on this apparent asymmetry between the Dirac and the K-G cases. Rather surprisingly, our result indicates a close parallelism between both spin-1/2 and spin-(0,1) cases, brought about by the Kemmer-Duffin [8] formalism [13] for integral spin as a natural counterpart to the Dirac equation for spin-1/2.…”