--- a/.gitmodules
+++ b/.gitmodules
@@ -19,4 +19,7 @@
 [submodule "javascripts/sigma"]
 	path = javascripts/sigma
 	url = https://github.com/jacomyal/sigma.js.git
+[submodule "javascripts/bubbletree"]
+	path = javascripts/bubbletree
+	url = https://github.com/okfn/bubbletree.git