unitex version specification

README.md

@@ -32,7 +32,7 @@ apt-get install python-setuptools
 apt-get install python-yaml
 ```
 
-Once you have met these requirements and downloaded the [Unitex](http://igm.univ-mlv.fr/~unitex/index.php?page=3&html=download.html) source distribution, run (as root):
+Once you have met these requirements and downloaded the [Unitex](http://igm.univ-mlv.fr/~unitex/index.php?page=3&html=download.html) source distribution (for Unitex >= 3.1), run (as root):
 
 ```bash
 UNITEX_INC=/path/to/unitex/Src/C++ python setup.py install