function mail(m1, m2, t1, t2)
{
  document.write('<a class="extern" href="mailto:' + m1 + '@' + m2 + '">');
  if (t1) document.write(t1);
  else document.write(m1 + '@' + m2);
  if (t2) document.write('@' + t2);
  document.write('</a>');
}