diff --git a/ThreeDee.xcworkspace/contents.xcworkspacedata b/ThreeDee.xcworkspace/contents.xcworkspacedata
index 94b2795..3f1b3b2 100644
--- a/ThreeDee.xcworkspace/contents.xcworkspacedata
+++ b/ThreeDee.xcworkspace/contents.xcworkspacedata
@@ -1,4 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Workspace
    version = "1.0">
+   <FileRef
+      location = "group:Math/Math.xcodeproj">
+   </FileRef>
 </Workspace>