\begin{tabbing}
(\=(((D 0) \+
\\[0ex]C\=ollapseTHENM (Backchain \+
\\[0ex]``sq\_stable\_\_from\_stable stable\_\_not``))$\cdot$) 
\\[0ex]
\-\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 3:n)) (first\_tok :t
\-\\[0ex]) inil\_term)))$\cdot$
\end{tabbing}