\documentstyle[11pt]{article}
\newcommand{\beqa}{\begin{eqnarray}}
\newcommand{\eeqa}{\end{eqnarray}}
\begin{document}
\centerline{\bf Trace Formulas}
\beqa
\gamma_\mu \gamma^\mu & = & 4 \nonumber\\
\gamma_\mu \!\not\!a \gamma^\mu & = &-2\, \!\not\!a \nonumber\\
\gamma_\mu \!\not\!a \!\not\!b \gamma^\mu & = &4\, a . b \nonumber\\
\gamma_\mu \!\not\!a \!\not\!b \!\not\!c \gamma^\mu & = &
-2\,\!\not\!c \!\not\!b \!\not\!a \nonumber\\
\nonumber\\
{\rm Tr} \!\not\!a  \!\not\!b & = & 4\, a . b \nonumber\\
{\rm Tr} \!\not\!a  \!\not\!b \!\not\!c  \!\not\!d & = & 
4\left( a . b\, c .d - a . c\, b . d + a . d\, b. c \right) \nonumber\\
{\rm Tr} \gamma_5 \!\not\!a  \!\not\!b \!\not\!c  \not\!d & = & 
4\, i \epsilon_{\mu\nu\lambda\sigma}
a^\mu b^\nu c^\lambda d^\sigma \nonumber\\
{\rm Tr} \gamma^\mu  \!\not\!p \gamma^\nu  \!\not\!k & = & 
4\left( p^\mu k^\nu +p^\nu k^\mu - p . k\, g^{\mu\nu} \right) \nonumber\\
{\rm Tr}\left[\gamma^\mu \left(1-\gamma_5\right) \!\not\!p \gamma^\nu
  \left(1-\gamma_5\right) \!\not\!k\right] & = &
2\,{\rm Tr} \gamma^\mu  \!\not\!p \gamma^\nu  \!\not\!k\, 
+ \,8 \, i \epsilon^{\mu\alpha\nu\beta}
p_\alpha k_\beta \nonumber\\
{\rm Tr}\left( \gamma^\mu \!\not\!p_1 \gamma^\nu  \!\not\!p_2\right)
{\rm Tr} \left(\gamma_\mu \!\not\!p_3 \gamma_\nu \!\not\!p_4 \right)
& = & 
32\left( p_1 . p_3\, p_2 .p_4 + p_1 . p_4\, p_2 . p_3 \right) \nonumber\\
\nonumber
\eeqa
\end{document}