function plus(divID){
        var obj = document.getElementById(divID);
        obj.style.display = 'block';
}

function minus(divID){
        var obj = document.getElementById(divID);
        obj.style.display = 'none';
}

function closeAll(parent_id){
  
  var parentElement = document.getElementById(parent_id);
  
  var elements = new Array();
  
  elements = parentElement.getElementsByTagName('li');
  
  for(var i = 0; i < elements.length; i++) {
    elements[i].style.display = 'none';
  }
}