function getPrevUrl() {
  head = document.getElementsByTagName('head')[0];
  links = head.getElementsByTagName('link');
  for (i = 0; i < links.length; i++) {
    if (String(links[i].rel).toLowerCase() == "prev") {
      return links[i].href;
    }
  }
  return false;
}

function getNextUrl() {
  head = document.getElementsByTagName('head')[0];
  links = head.getElementsByTagName('link');
  for (i = 0; i < links.length; i++) {
    if (String(links[i].rel).toLowerCase() == "next") {
      return links[i].href;
    }
  }
  return false;
}

function link(ev) {
  var code;
  if (!ev) var ev = window.event;
  if (ev.keyCode) code = ev.keyCode;
  else
    if (ev.which) code = ev.which;
  if ((code == 37) && (ev.ctrlKey == true))
    if (getPrevUrl())
      location.href = getPrevUrl();
  if ((code == 39) && (ev.ctrlKey == true))
    if (getNextUrl())
      location.href = getNextUrl();
}