Pick one or two, other than the first, of the solutions (4-20) and show that for p1=0, p2=p3=0, a particle, which would be in a z direction (up) spin eigenstate if p were zero, will not be in that up spin eigenstate. Then show, for the same solutions chosen, but with p1=p2=0, p3=0 as seen in the lab, that the particle is in the same spin eigenstate as it would be if p were zero.