diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 00000000..c11fcec9
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "book"]
+	path = book
+	url = https://gitea.networkx.de/rzerres/element-call-book.git
diff --git a/book b/book
new file mode 160000
index 00000000..7c07dc59
--- /dev/null
+++ b/book
@@ -0,0 +1 @@
+Subproject commit 7c07dc59c40783183279b693d31eb74a4aed3914