anchor.diff:      }
   }
   
  -function updateDeleteControlVisibility(objectType, elts) {
  -    var controls = $$('.' + objectType + '-delete-control')
  +function updateDeleteControlVisibility(objectType, elts, containerId) {
  +    var controls = $$('#' + containerId + ' .' + objectType + '-delete-control')
  +    console.log(elts)
  +    console.log(controls)
       if (elts.length <= 1) {
           controls.each(function(c) { c.hide() })
       } else {
  
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:     var siblings = $$('div.epoch')
  
      updateMoveControlVisibility('epoch', thisEpoch.id.split('-')[1], thisEpoch, siblings)
      updateDeleteControlVisibility('epoch', siblings, 'epochs')
  }
  
  function updateAllEpochsControlVisibility() {
  