anchor.diff:      var siblings = $A(thisArm.parentNode.getElementsByTagName("LI"))
   
       updateMoveControlVisibility('arm', thisArm.id.split('-')[1], thisArm, siblings)
  -    updateDeleteControlVisibility('arm', siblings);
   }
   
   function updateAllArmsControlVisibility(epochId) {
  -    var armItems = $$('#epoch-' + epochId + '-arms li');
  +    _updateAllArmsControlVisibility('epoch-' + epochId + '-arms')
  +}
  +
  +function _updateAllArmsControlVisibility(eltId) {
  +    var armItems = $$('#' + eltId + ' li');
       armItems.each(updateArmControlVisibility)
  +    updateDeleteControlVisibility('arm', armItems, eltId);
   }
   
   function createStudyControls() {
  
positive.code: <%@page contentType="text/javascript" %>
  <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
  function createAllArmControls() {
      $$('#epochs li.arm').each(createArmControls)
  }
  
  function createArmControls(armItem) {
  
negative.code:     }
  }
  
  function updateDeleteControlVisibility(objectType, elts, containerId) {
      var controls = $$('#' + containerId + ' .' + objectType + '-delete-control')
      console.log(elts)
      console.log(controls)
      if (elts.length <= 1) {
          controls.each(function(c) { c.hide() })
      } else {
  