\begin{minipage}{7cm}
\begin{sf}
SURFACE EMISSION
\[
\mathbf{I^i(n,s_0)}=\frac{\mathbf{Q_kO(u_k,s_k)I_{surf}(n_k,u_k)}}{O_{11}(\mathbf{u_{k},s_k})\left(1-R_{11}\right)}
\]
\end{sf}
\end{minipage}
