\begin{align} & \left(\beta mc^{2}+c\left(\sum_{n=1}^{3}\alpha_{n}p_{n}\right)\right)\psi(x,t)=i\hbar\frac{\partial\psi(x,t)}{\partial t} \\ & i\hbar\gamma^{\mu}\partial_{\mu}\psi-mc\psi=0 \\ & (i{\partial}-m)\psi=0\par \\ \end{align}