\begin{equation}
I_{4 \times 4}, \gamma_5,

\alpha_x, \alpha_y, \alpha_z

\Sigma_x, \Sigma_y,  \Sigma_z

\beta \Sigma_x, \beta \Sigma_y, \beta \Sigma_z

i \beta \alpha_x, i \beta \alpha_y, i \beta \alpha_z
\end{equation}