<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:msub> <mml:mi mathvariant="bold-italic">U</mml:mi>
<mml:mi mathvariant="bold-italic">N</mml:mi>
</mml:msub>
<mml:mo mathvariant="bold" stretchy="false">(</mml:mo>
<mml:mi mathvariant="bold-italic">&#1009;</mml:mi>
<mml:mo mathvariant="bold">,</mml:mo>
<mml:mi mathvariant="bold-italic">&#977;</mml:mi>
<mml:mo mathvariant="bold" stretchy="false">)</mml:mo>
</mml:math>