diff --git a/book/_static/attribution.css b/book/_static/attribution.css
deleted file mode 100644
index 4c71166..0000000
--- a/book/_static/attribution.css
+++ /dev/null
@@ -1,4 +0,0 @@
-/* Set attribution admonition symbol, configuration part of TeachBooks package (https://teachbooks.io/manual/features/external_toc.html) */
-div.attribution > .admonition-title::after {
-  content: "\f10d";
-}