...
diff --git a/coders/webp.c b/coders/webp.c
index 9a376d5..cfd7ddd 100644
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -348,7 +348,8 @@
       *mux;
 
     /*
-      Extract any profiles.
+      Extract any profiles:
+      https://developers.google.com/speed/webp/docs/container-api.
     */
     content.bytes=stream;
     content.size=length;