function show_column(do_show) {

  var stl;
  if (do_show) stl = 'visible'
  else         stl = 'hidden';

  var tbl  = document.getElementById('articletext');
  var rows = tbl.getElementsByTagName('tr');

  for (var row=0; row<rows.length; row++) {
    var cells = rows[row].getElementsByTagName('td') 
    cells[2].style.visibility=stl;
  }
}