\begin{table}%t2
%\centering
\par
  \caption{References to literature data with spectroscopic, 
    astrometric, eclipsing, and visual binaries in Sco~OB2. 
    Using these data we
    find that 33 out of the 74 candidate companion stars in our dataset were
    already documented in literature, while 41 were previously unknown.
    \label{table: litlist}}
  \begin{tabular}{ll}
    \hline \hline 
    Reference & Detection method \\
    \hline
    \cite{alencar2003} & Spectroscopic \\
    \cite{balega1994} & Visual \\
    \cite{barbier1994} & Spectroscopic\\
    \cite{batten1997} & Spectroscopic \\ %\cite{batten1989} \\
    \cite{couteau1995} & Combination\\
    The Double Star Library & Combination\\
    \cite{duflot1995} &Spectroscopic\\
    \cite{hartkopf2001} &Visual\\ %\cite{hartkopf1999} \\
    \cite{jordi1997} &Eclipsing\\
    The {\it Hipparcos} and {\it Tycho} Catalogues &Astrometric\\ 
    \cite{kraicheva1989} &Spectroscopic\\ %\cite{kraicheva1980} \\
    \cite{malkov1993} &Combination \\
    \cite{mason1995} &Visual \\
    \cite{mcalister1993} &Visual\\
    Miscellaneous, e.g. SIMBAD &Combination\\
    \cite{miura1992} &Visual\\
    \cite{pedoussaut1996} &Spectroscopic\\ %\cite{pedoussaut1985} \\
    \cite{shatsky2002} &Visual\\
    \cite{sowell1993} &Visual\\
    \cite{svechnikov1984} &Combination\\
    \cite{tokovinin1997} &Combination\\
    \cite{worley1997} &Combination\\
    \hline 
  \end{tabular}
  \end{table}