Index: /reasoner/reasoner.tex
===================================================================
--- /reasoner/reasoner.tex	(revision 61)
+++ /reasoner/reasoner.tex	(revision 62)
@@ -849,4 +849,5 @@
     \item \textbf{Reuse visitor instances} if applied more than once, in particular reasoners with more complex internal data structures such as maps or lists. This required some refactoring of the IVML model implementation.
     \item \textbf{Avoid} iterators, temporary constraint creation, temporary data structures wherever possible.
+    \item \textbf{Avoid} multipe variable substitutions per constraint expressions, i.e., join variable substitutions wherever possible. Variable substitution copies the expression. Multiple copies throws away the last copied expression.
 \end{itemize}