Dhtmlxcombo is not defined error

Hello. I’m using dhtmlxcombo to make basic combobox.
Even initialize combo, it thorws error. Here is my code.

[code]

	<script src="/Scripts/ext/dhtmlxgrid_filter.js" type="text/javascript" charset="utf-8"></script>

    <link rel="stylesheet" href="/Scripts/dhtmlxgrid.css" type="text/css" media="screen" charset="utf-8">
	<link rel="stylesheet" href="/Scripts/dhtmlcombo.css" type="text/css" media="screen" charset="utf-8">
    <link rel="stylesheet" href="/Scripts/skins/dhtmlxgrid_dhx_skyblue.css" type="text/css" media="screen" charset="utf-8">
    
</head>
<body>
    <div id="grid_here" style="width:600px; height:400px;">
    </div>
    <script type="text/javascript" charset="utf-8">
        var grid = new dhtmlXGridObject("grid_here");
           grid.setImagePath("/Scripts/imgs/");
           grid.setHeader("Author, Title");
           grid.attachHeader("#text_filter,#text_filter");
           grid.setColumnIds("author,title");
           grid.setInitWidths("100,*");
           grid.setSkin("dhx_skyblue");
           grid.init();
           grid.load("/Admin/Data?=" + grid.uid());

           grid.filterBy(0, "");

           dp = new dataProcessor("/Admin/Save");
           dp.setTransactionMode("POST", false);
           dp.enableDataNames(true);
           dp.init(grid);

           function clear_filter() {
            grid._f_rowsBuffer = null; //reset cache	
           }

           function add() {
           	clear_filter();
           	grid.addRow(grid.uid(), 'new user');
           }

           function del() {
           	clear_filter();
           	grid.deleteSelectedRows(); //initialize ( - ) mark.
           }

    </script>
	<input type="button" value="Add" onclick="add();">
    <input type="button" value="Delete" onclick="del();">

	<select style='width:200px;'  id="combo_zone1" name="alfa1">
		<option value="1">a00</option>
		<option value="2">a01</option>
	</select>
	<script type="text/javascript">
		var z = dhtmlxComboFromSelect("combo_zone1");
	</script>
	<script type="text/javascript">
		
	</script>
</body>

Hello
What DHTMLX version do you use?