<keyword>intro</keyword>
<keyword>intros</keyword>
<keyword>lapply</keyword>
+ <keyword>left</keyword>
<keyword>letin</keyword>
<keyword>normalize</keyword>
<keyword>reduce</keyword>
<keyword>replace</keyword>
<keyword>rewrite</keyword>
<keyword>ring</keyword>
+ <keyword>right</keyword>
<keyword>symmetry</keyword>
<keyword>simplify</keyword>
<keyword>split</keyword>