Testing 2
Testing . . .
QED Lagrangian Density
\newcommand{\uI}{\mathrm{i}}
\newcommand{\commute}[2]{\left[{#1}\!
\mathrel{\vphantom{{#1}},\vphantom{{#2}}
\kern-\nulldelimiterspace}\!{#2}\right]}
\newcommand{\anticommute}[2]{\left\{{#1}\!
\mathrel{\vphantom{{#1}},\vphantom{{#2}}...