    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE language SYSTEM "language.dtd"
    [
        <!-- comment line 1
             comment line 2 -->
        <!ENTITY name    "(?![0-9])[\w_:][\w.:_-]*">
        <!ENTITY entref  "&amp;(#[0-9]+|#[xX][0-9A-Fa-f]+|&name;);">
    ]>
    <element attr1="a1" attr2="2.03" attr3="&entity;">
        <sub-element/>
    </element>

    <wrong<very wrong>>