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\begin{table}[tbp]
  \caption{ML trials: scoring one category per document}
  \begin{center}
    \small
    \begin{tabular}{lc|rrr|rrr}
      \hhline{========}
      Documents & Threshold & \multicolumn{3}{c}{traditional \%} &
      \multicolumn{3}{|c}{BDM \%} \\
      & & $P$ & $R$ & $F_1$   & $AP$ & $AR$ & $AF_1$\\
      \hhline{--------}
      Abstracts & 0.1 & 27.2  & {\slugc}29.5  & {\slugc}28.3  & 29.5  & {\slugc}29.5  & {\slugc}29.5  \\
      Abstracts \& HTMLs & 0.1  & 47.8  & 47.8  & 47.8  & 66.8  & 66.8  & 66.8  \\
      \hhline{--------}
      Abstracts \& HTMLs & 0.3 & 68.0  & 40.9  & 50.7  & 74.1  & 51.0  & 60.4  \\
                         & 0.5 & 85.3  & 19.8  & 31.4  & 88.1  & 29.6  & 44.3  \\
                         & 0.8 & 97.9  &  8.1  & 14.7  & 98.3  & 17.7  & 30.0  \\
      \hhline{========}
    \end{tabular}
  \end{center}
  \label{tab:ml-initial}
\end{table}
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