diff --git a/doc/README.md b/doc/README.md
index c7aed4e..3a04e2b 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -72,7 +72,7 @@ export DISPLAY=":0.0"
 
 ## notes
 
-Monitor files while developing to restart Processing sketch on save with `entr`. After running the sketch in one terminal with `processing-runsketch_IF3.sh`, in another terminal run something like 
+Monitor files while developing to restart Processing sketch on save with [`entr`](http://entrproject.org/). After running the sketch in one terminal with `processing-runsketch_IF3.sh`, in another terminal run something like 
 ```
 ls PROJECTS/IF3Si/pde/IF3Si/*.pde | entr killall java
 ```