window.addEvent('domready', function() {
	$('book').addEvent('change',function() {
		var xmlHTTP = new Request({url: "/retrieve_data.php",method:'get',
								  onComplete:function(txt,xml) {
			if(xml.childNodes.length > 0) {
				if(xml.childNodes[0].firstChild.nodeName.toUpperCase()!="ERROR") {
					$('chapter').options.length = 0;
					for(i=0;i<xml.childNodes[0].childNodes.length;i++) {
						var chapterOpt = new Element('option',{
								'value': getNodeText(xml.childNodes[0].childNodes[i]),
								'text': getNodeText(xml.childNodes[0].childNodes[i])
						});
						$('chapter').adopt(chapterOpt);
					}
				} else {
					alert("Error: " + getNodeText(xml.childNodes[0].firstChild));
				}
			} else {
				alert("Error: Could not communicate with server.");
			}
		}.bind(this)});
		xmlHTTP.send("action=retrieveChapters&book=" + $('book').value + '&ms=' + new Date().getTime());
	});
});