function getPredefinedAOList(courseName, gradeLevel, pageSize, pageIndex){
    
    var httpReq = getHTTPReqObject();
    var res = null;
    
    // send request
    httpReq.open('POST', "../" + proxyURL, true );
    httpReq.setRequestHeader('Content-Type','application/x-www-form-urlencoded'); 
    
    httpReq.onreadystatechange = function () {
        if (httpReq.readyState == 4 && httpReq.status == 200) {
            if(res != httpReq.responseText) {
                var res = httpReq.responseText;
                document.getElementById("lolist").innerHTML = res;
            }
        }
    }
    
    httpReq.send(
        'exoperation='+'predefined'
        + '&'
        + 'operation='+ 'proxy'
        + '&'
        + 'pageIndex=' + pageIndex
        + '&'
        + 'pageSize=' + pageSize
        + '&'
        + 'c=' + courseName
        + '&'
        + 'g=' + gradeLevel
        );

}