求用XSLT样式表实现如下XML格式转换

原XML文件 目的是先按year分组，然后再在year中按照typeid分组
<?xml version="1.0" encoding="GB2312"?>
<catalog>
    <cd>
        <title>Empire Burlesque </title>
        <typeid>001 </typeid>
        <year>1985 </year>
    </cd>
    <cd>
        <title>Hide your heart </title>
        <typeid>002 </typeid>
        <year>1985 </year>
    </cd>
    <cd>
        <title>Still got the blues </title>
        <typeid>001 </typeid>
        <year>1986 </year>
    </cd>
</catalog>
要求转成如下格式：
<?xml version="1.0" encoding="GB2312"?>
<Result>
    <Year id = "1985">
        <Typeid num = "001">
<title>Empire Burlesque </title>
        </Typeid>
        <Typeid num = "002"