diff --git a/README.txt b/README.txt
index f514b19e1dac49dbc82b096745fd5f33abd27823..46ac724de67805d8391968acf5e8c8420d6f785f 100644
--- a/README.txt
+++ b/README.txt
@@ -6,6 +6,7 @@ Documentation:
   M. Folschette,
   The Hoare-fol Tool,
   technical report, 2019.
+  https://hal.archives-ouvertes.fr/hal-02409801v1
 
 Principle:
   This implementation defines grammars and trees to represent properties on