Remarks concerning a proposed two-component spin-1/2 wave equation

Two-component equations of the form proposed by Biedenharn, Han, and van Dam are discussed for the case in which the parity operator is strictly internal. It is shown that these equations lack conventional translation and Lorentz invariance. The connection between these equations and the Dirac equation is discussed and it is shown that the solutions of the Dirac equation may be constructed from the solutions of one of the two-component equations.