diff --git a/Makefile b/Makefile
index 9d532a4..7e572d9 100644
--- a/Makefile
+++ b/Makefile
@@ -87,3 +87,13 @@
 swagger: xos
 	pushd repos/xos/docs; make swagger_docs; popd;
 
+# generate a list of git checksums suitable for updating git_refs
+freeze: repos
+	@for repo in $(OTHER_REPO_DOCS) ; do \
+	  GIT_SUBDIR=`grep "^$$repo " git_refs | awk '{print $$2}'` ;\
+	  cd "repos/$$repo" > /dev/null ;\
+	    HEAD_SHA=`git rev-parse HEAD` ;\
+	    printf "%-21s %-8s %-40s\n" $$repo $$GIT_SUBDIR $$HEAD_SHA ;\
+	  cd ../.. ;\
+	done
+
diff --git a/book.json b/book.json
index fd3f609..1317bf7 100644
--- a/book.json
+++ b/book.json
@@ -21,6 +21,10 @@
           "text": "Master (Devel)"
         },
         {
+          "value": "/cord-6.0",
+          "text": "6.0 (Stable)"
+        },
+        {
           "value": "/cord-5.0",
           "text": "5.0 (Stable)"
         },
@@ -29,10 +33,6 @@
           "text": "4.1 (Stable)"
         },
         {
-          "value": "/cord-4.0",
-          "text": "4.0 (Stable)"
-        },
-        {
           "value": "https://wiki.opencord.org/display/CORD/Building+and+Installing+CORD",
           "text": "3.0 and previous (wiki)"
         }