diff --git a/pointprocesses/exercises/pointprocesses01.tex b/pointprocesses/exercises/pointprocesses01.tex
index 1139ead..15cc5a2 100644
--- a/pointprocesses/exercises/pointprocesses01.tex
+++ b/pointprocesses/exercises/pointprocesses01.tex
@@ -173,7 +173,7 @@ jan.benda@uni-tuebingen.de}
       \colorbox{white}{\includegraphics[width=1\textwidth]{isihist}}
     \end{solution}
   
-    \part Write a function that computes and plots the serial
+    \part XXX Add return map!!! XXX Write a function that computes and plots the serial
     correlations of interspike intervals for lags upto
     \code{maxlag}. The serial correlations $\rho_k$ for lag $k$ of the
     interspike intervals $T_i$ are the correlation coefficients