\begin{tabbing}
(\=(((((Symmetry) \+
\\[0ex]CollapseTHEN (HypSubst ({-}1) 0))$\cdot$) 
\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 
\-\\[0ex]1\=:n) ((first\_nat 1:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$) \+
\\[0ex]CollapseTHEN (((
\-\\[0ex]B\=ackThruLemma `append\_firstn\_lastn`) \+
\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 1:n
\-\\[0ex]) ((first\_nat 2:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$))$\cdot$
\end{tabbing}