diff --git a/Makefile b/Makefile
index adb47bb..29f1967 100644
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,7 @@ bulma:
 	cp tmp/bulma/css/bulma.css.map css/bulma.css.map
 	cp tmp/bulma/css/bulma.min.css css/bulma.min.css
 
+# https://nimiq.github.io/qr-creator/
 .PHONY: qr-creator
 qr-creator:
 	curl -Lsf https://unpkg.com/qr-creator@1.0.0/dist/qr-creator.es6.min.js -o js/qr-creator.es6.min.js