Doc: add aliasing in common pitfaffs.

doc/Pitfalls.dox

diff --git a/doc/Pitfalls.dox b/doc/Pitfalls.dox
index cf42eff..3f39505 100644
--- a/doc/Pitfalls.dox
+++ b/doc/Pitfalls.dox
@@ -2,10 +2,16 @@
 
 /** \page TopicPitfalls Common pitfalls
 
+
 \section TopicPitfalls_template_keyword Compilation error with template methods
 
 See this \link TopicTemplateKeyword page \endlink.
 
+\section TopicPitfalls_aliasing Aliasing
+
+Don't miss this \link TopicAliasing page \endlink on aliasing,
+especially if you got wrong results in statements where the destination appears on the right hand side of the expression.
+
 \section TopicPitfalls_auto_keyword C++11 and the auto keyword
 
 In short: do not use the auto keywords with Eigen's expressions, unless you are 100% sure about what you are doing. In particular, do not use the auto keyword as a replacement for a Matrix<> type. Here is an example: