one more lemma we'll need

paper/gtt.tex

@@ -1044,7 +1044,7 @@ is our graduality theorem.
   \begin{mathpar}
     \inferrule
     {A \ltdyn A'}
-    {}
+    {\cdots}
   \end{mathpar}
 \end{lemma}
 
@@ -1092,6 +1092,11 @@ Finally, we reach the case-by-case proof of the graduality lemma.
   \end{enumerate}
 \end{lemma}
 
+\begin{lemma}[Graduality Substitution Principles]
+  TODO: substituting value in a value, term or stack, substituting a
+  term in a stack (use substitution for the target, decomposition)
+\end{lemma}
+
 \begin{figure}
   \begin{mathpar}
   \begin{array}{rcl}