Display:

<mmultiscripts> base (subscript superscript)* [ <mprescripts/> (presubscript presuperscript)* ] </mmultiscripts>

Source:

<mmultiscripts>
<emph>base</emph> (
<emph>subscript superscript</emph>)* [ &lt;mprescripts/> (
<emph>presubscript presuperscript</emph>)* ] &lt;/mmultiscripts>