1 files changed, 2 insertions, 0 deletions
diff --git a/main.tex b/main.tex
index 6d133be..ba35e1f 100644
--- a/main.tex
+++ b/main.tex
@@ -204,6 +204,8 @@ coupling to linear order is
 \begin{equation}
   f_\i=-b^{(i)}\epsilon_\X^{(i)}\eta.
 \end{equation}
+Many high-order interations are permitted, and in the appendix another of the
+form $\epsilon^2\eta^2$ is added to the following analysis.
 If there exists no component of strain that transforms like the representation
 $\X$ then there can be no linear coupling. The next-order coupling is linear in
 strain, quadratic in order parameter, and the effect of this coupling at a