\begin{table}%t2
  %\centering
\par
   \caption{Non-linear algorithm codes, (characters 6--8 of
      \CTYPE{k\Ci}).}
   \begin{tabular}{lll}
      \hline\hline
                 & Regularly      &                \\
      Code       & sampled in     & Expressed as   \\
      \hline
      \keyv{F2W} & Frequency      & Wavelength     \\
      \keyv{F2V} & Frequency      & Apparent radial velocity\\
      \keyv{F2A} & Frequency      & Air wavelength \\
      \keyv{W2F} & Wavelength     & Frequency      \\
      \keyv{W2V} & Wavelength     & Apparent radial velocity \\
      \keyv{W2A} & Wavelength     & Air wavelength \\
      \keyv{V2F} & Apparent radial velocity  & Frequency      \\
      \keyv{V2W} & Apparent radial velocity  & Wavelength     \\
      \keyv{V2A} & Apparent radial velocity  & Air wavelength \\
      \keyv{A2F} & Air wavelength & Frequency      \\
      \keyv{A2W} & Air wavelength & Wavelength     \\
      \keyv{A2V} & Air wavelength & Apparent radial velocity \\
      \hline
      \keyv{LOG} & logarithm &
                                Any 4-letter coordinate type \\
      \keyv{GRI} & detector &
                                Any from Table~\ref{ta:codes}\\
      \keyv{GRA} & detector &
                                Any from Table~\ref{ta:codes}\\
      \keyv{TAB} & not regular &
                                Any 4-letter coordinate type \\
      \hline
   \end{tabular}
   \label{ta:NLcodes}
\end{table}