diff --git a/README.md b/README.md
index fc092a1..6bae9b8 100644
--- a/README.md
+++ b/README.md
@@ -122,7 +122,9 @@ Installation
 
 Requirements: Python 3.9.
 
-To install all packages, run:
+  * Install [cairo 2D graphic library](https://www.cairographics.org/download/),
+  * install Python packages:
+
 
 ```bash
 pip install -r requirements.txt
diff --git a/doc/readme.moi b/doc/readme.moi
index 7eafd44..4aa2bd1 100644
--- a/doc/readme.moi
+++ b/doc/readme.moi
@@ -170,7 +170,9 @@ Every way and node displayed with the random color picked for each author with \
 
 Requirements\: Python 3.9/* or higher*/.
 
-To install all packages, run\:
+\list
+    {Install \ref {https://www.cairographics.org/download/} {cairo 2D graphic library},}
+    {install Python packages\:}
 
 \code {pip install -r requirements.txt
 pip install .} {bash}