\begin{table}%t1
\par
\caption {\label{Tab:sample}The four observing campaigns defining the four (sub)samples  of Hipparcos M~giants.}
%\centerline
 {\begin{tabular}{ccccc}
\hline
\hline
Sample         & I & II & III & IV\\
\hline
Selection      & 2 measurements in Famaey et al.~(2005) &
$\sim$1/3 of I & all $\sigma(V_r) > 1$~\kms\ from II &  $\sigma(V_r) <  1$~\kms\ from II \\               &   &    &   & $0^h \le \alpha \le 16.5^h$ \\  
$N_{\rm star}$ & 771 & 254 & 35 & 138\\
$N_{\rm meas}$ per star  & 2 & ${\ge} 4^a$ &   $\ge 5$ & $N$(II)~+~1\\
Telescope      & Swiss 1-m (OHP) & Swiss 1-m (OHP) & 1.93-m (OHP) & 1.93-m (OHP)\\
Spectrograph   & CORAVEL & CORAVEL & ELODIE & ELODIE \\
Time span      & 1991--1999 & 1993--1995 & 2000--2004 & 2001--2004\\
\hline
\end{tabular}}
\par
\smallskip
$^a$ Seven stars have $N_{\rm meas} = 3$.
\end{table}