diff --git a/Dockerfile b/Dockerfile
index 119b295..7aa1dca 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,3 +1,4 @@
+# <https://gitlab.com/ydkn/docker-cups>
 FROM ydkn/cups:latest
 
 ARG BROTHER_HLL3230CDW_DRIVER=/tmp/hll3230cdwpdrv-1.0.2-0.i386.deb