```
% pandoc -f docbook -t latex
<equation>
  <mathphrase>
    J(x, y) = \left\{ \begin{array}{ll}
    0 &amp; \text{if $I(x, y) &lt; t$} \\
    1 &amp; \text{if $I(x, y) \ge t$}
    \end{array}
    \right.
  </mathphrase>
</equation>
^D
\[
    J(x, y) = \left\{ \begin{array}{ll}
    0 & \text{if $I(x, y) < t$} \\
    1 & \text{if $I(x, y) \ge t$}
    \end{array}
    \right.
  \]
```