diff --git a/NOTES.md b/NOTES.md
index 9cf98e51c..1cbbef6c5 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -80,3 +80,27 @@ which refer to elements, so we want to have real references of those
 elements, but we don't have the data yet. Thus when the Connection
 encounters a new object but has a non-loaded representation of it,
 the non-loaded version is replaced.
+
+## Prior Art
+
+JOSM and Potlatch 2 appear to implement versioning in the same way, but having
+an undo stack:
+
+```java
+// src/org/openstreetmap/josm/actions/MoveNodeAction.java
+Main.main.undoRedo.add(new MoveCommand(n, coordinates));
+
+// src/org/openstreetmap/josm/command/MoveCommand.java
+
+/**
+ * List of all old states of the objects.
+ */
+private List<OldState> oldState = new LinkedList<OldState>();
+
+@Override public boolean executeCommand() {
+// ...
+}
+@Override public void undoCommand() {
+// ...
+}
+```
diff --git a/js/iD/Node.js b/js/iD/Node.js
index 8ef6a617e..927d69927 100644
--- a/js/iD/Node.js
+++ b/js/iD/Node.js
@@ -8,7 +8,6 @@ iD.Node = function(id, lat, lon, tags, loaded) {
 };
 
 iD.Node.prototype = {
-
     type: 'node',
 
     intersects: function(extent) {
@@ -17,5 +16,4 @@ iD.Node.prototype = {
             (this.lat <= extent[0][1]) &&
             (this.lat >= extent[1][1]);
     }
-
 };
diff --git a/js/iD/Relation.js b/js/iD/Relation.js
index 9e8968732..a72968e9f 100644
--- a/js/iD/Relation.js
+++ b/js/iD/Relation.js
@@ -11,5 +11,3 @@ iD.Relation.prototype = {
 
     intersects: function() { return true; }
 };
-
-// iD.Util.extend(iD.Relation, iD.Entity);