var   ref_iterator_1=1;
var   ref_iterator_2=2;
   $(document).ready(function(){
      ref = $('#references').children();
      ref.filter(':nth-child(1)').show();
      ref.filter(':nth-child(2)').show();
      setInterval(changeRef,5000);
      });
   function changeRef(){
      var len = ref.length;
   
      ref.filter(':nth-child('+ref_iterator_1+')').hide();
      ref.filter(':nth-child('+ref_iterator_2+')').hide();
      if (ref_iterator_1<len-1){
         ref_iterator_1+=2;
         ref_iterator_2+=2;
      }
      else{
         ref_iterator_1=1;
         ref_iterator_2=2;
      }
      
      ref.filter(':nth-child('+ref_iterator_1+')').show();
      ref.filter(':nth-child('+ref_iterator_2+')').show();
   }