\begin{tabbing}
(\% Prove inductive hypothesis \% 
\\[0ex](\=(((HypSubst 12 14) \+
\\[0ex]CollapseTHENM (InstHyp [$f$(${\it y'}$);${\it y'}$
\-\\[0ex]]\= 10))$\cdot$) \+
\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 3:n
\-\\[0ex])) (first\_tok :t) inil\_term)))$\cdot$)
\end{tabbing}