[<emphasis role="bold">depth=</emphasis><emphasis><link linkend="grammar.nat">nat</link></emphasis>]
<emphasis><link linkend="grammar.sterm">sterm</link></emphasis>
[<emphasis role="bold">to</emphasis>
[<emphasis role="bold">depth=</emphasis><emphasis><link linkend="grammar.nat">nat</link></emphasis>]
<emphasis><link linkend="grammar.sterm">sterm</link></emphasis>
[<emphasis role="bold">to</emphasis>