function switchBookCover(side)
{
  if(side == 'back')
  {
    findObj('backcover').style.display = 'none';
    findObj('backcover').style.visibility = 'hidden';
    findObj('frontcover').style.display = 'block';
    findObj('frontcover').style.visibility = 'visible';
  }
  if(side == 'front')
  {
    findObj('frontcover').style.display = 'none';
    findObj('frontcover').style.visibility = 'hidden';
    findObj('backcover').style.display = 'block';
    findObj('backcover').style.visibility = 'visible';
  }
}

function findObj(theObj,theDoc)
{
  var p, i, foundObj;

  if(!theDoc)
  {
    theDoc = document;
  }
  if( (p = theObj.indexOf('?')) > 0 && parent.frames.length)
  {
    theDoc = parent.frames[theObj.substring(p+1)].document;
    theObj = theObj.substring(0,p);
  }
  if(!(foundObj = theDoc[theObj]) && theDoc.all)
  {
    foundObj = theDoc.all[theObj];
  }
  for(i=0; !foundObj && i < theDoc.forms.length; i++)
  {
    foundObj = theDoc.forms[i][theObj];
  }
  for(i=0; !foundObj && theDoc.layers && i < theDoc.layers.length; i++)
  {
    foundObj = findObj(theObj,theDoc.layers[i].document);
  }
  if(!foundObj && document.getElementById)
  {
    foundObj = document.getElementById(theObj);
  }

  return foundObj;
}