C - 0x3F, 0x41 - 0x5A, and 0x61 -
    0x7A.</p>
    <p>
    Documents should not use
    UTF-32,
    JIS_C6226-1983,
    JIS_X0212-1990,
    HZ-GB-2312,
    JOHAB (Windows code page 1361),
    encodings based on ISO-2022,
    or encodings based on EBCDIC.</p>
    <p>Documents
    <a href="terminology.html#must-requirement" id="must-requirement_xref21">must</a>
    not use
    CESU-8,
    UTF-7,
    BOCU-1,
    or SCSU
    encodings.</p>
    <p>In a
    <a href="documents.html#syntax-document-xml" id="syntax