included VTN page in SUMMARY

Change-Id: I04f188fcf3f872ff23857abecbe8d0a858ed80ae
diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
index 43302b6..2835e92 100644
--- a/docs/SUMMARY.md
+++ b/docs/SUMMARY.md
@@ -31,13 +31,13 @@
     * [Writing Synchronizers](xos/dev/synchronizers.md)
         * [Design Guidelines](xos/dev/sync_arch.md)
         * [Implementation Details](xos/dev/sync_impl.md)
-    * [Migrating Models to 4.0](xos/migrate_4.0.md)
 * [Developing for CORD](develop.md)
     * [Getting the Source Code](getting_the_code.md)
     * [Workflow: Mock/Single Scenario](xos/dev/workflow_mock_single.md)
     * [Workflow: Local Scenario](xos/dev/workflow_local.md)
     * [Workflow: CiaB Scenario](xos/dev/workflow_pod.md)
     * [TOSCA Development](platform-install/bootstrap_models_in_xos.md)
+    * [VTN and Service Composition](xos/xos_vtn.md)
     * [Tutorials](xos/tutorials/tutorials.md)
         * [Example Service](xos/tutorials/example_service.md)
         * [Synchronizer in the local scenario](xos/tutorials/local_synchronizer_dev_loop.md)