<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mi>f</mml:mi>
<mml:mo class="MathClass-punc">:</mml:mo>
<mml:mi mathvariant="double-struck">T</mml:mi>
<mml:mo class="MathClass-rel">&#8594;</mml:mo>
<mml:mi>R</mml:mi>
</mml:math>