diff --git a/docs/stylesheets/extra.css b/docs/stylesheets/extra.css
index 73db8469..2ea440b2 100644
--- a/docs/stylesheets/extra.css
+++ b/docs/stylesheets/extra.css
@@ -1,3 +1,7 @@
+/* Copyright 2024 ETH Zurich and University of Bologna. */
+/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
+/* SPDX-License-Identifier: Apache-2.0 */
+
 :root {
   --md-primary-fg-color:        #02793C;
   --md-primary-fg-color--light: #21B42A;