var amazon_lo_images;
  var amazon_hi_images;
        
  function setup_amazon_images(numberofreferences) {
      
      amazon_lo_images = new Array(numberofreferences);
      amazon_hi_images = new Array(numberofreferences);
      
      for (var i = 0;  i < numberofreferences;  i++) {
          amazon_lo_images[i] = new Image();
          amazon_lo_images[i].src = "../images.two.state/buybookslo.png";
          amazon_hi_images[i] = new Image();
          amazon_hi_images[i].src = "../images.two.state/buybookshi.png";
      }
  }
     
  function amazon_buttonhi(referencename) {
      var  AMAZON_REFERENCE_LENGTH = "amazonreference".length;
      var  referencestring =  referencename.substr(AMAZON_REFERENCE_LENGTH);
      var  referencenumber =  parseInt(referencestring); 
      referencenumber = referencenumber - 101;
      document[referencename].src = amazon_hi_images[referencenumber].src;
  }
  
  function amazon_buttonlo(referencename)   {
      var  AMAZON_REFERENCE_LENGTH = "amazonreference".length;
      var  referencestring =  referencename.substr(AMAZON_REFERENCE_LENGTH);
      var  referencenumber =  parseInt(referencestring); 
      referencenumber = referencenumber - 101;
      document[referencename].src = amazon_lo_images[referencenumber].src;
  }