Daseian notation
...that the earliest known examples of polyphonic music, dating from the 9th century, are written in Daseian notation?
...that the earliest known examples of <a class="mw-redirect" href="./Polyphonic_music" id="mwDEY" rel="mw:WikiLink" title="Polyphonic music">polyphonic music</a>, dating from the 9th century, are written in <b id="mwDEc"><a href="./Daseian_notation" id="mwDEg" rel="mw:WikiLink" title="Daseian notation">Daseian notation</a></b>?