\begin{table}%t1
 % \tabcolsep=3pt
\par
    \caption{\label{table parameters}A not complete overview of recent values of parameters
      describing the GB, its bar and the distance to the
      GC.}
    %\centerline
{
       \small \begin{tabular}{lllllll}
      \hline\hline
      Reference & $R_0$ & $a_m$ & $a_0$ & 1:$\eta$:$\zeta$ & $\phi$ &
      Based on \\
      & [kpc] & [kpc] & [pc] & & [\deg] & \\
      \hline
      \citet{Fernley1987} & 8.0 $\pm$ 0.65 & & & & & RR~Lyrae stars\\
      \citet{Reid1988} & 7.1 $\pm$ 1.5 & & & & & H$_2$O maser spots\\
      \citet{Whitelock1992} & 9.1 & & & 1:0.25:0.25 & 45 & Mira   variables \\
      \citet{Dwek1995} & & & & 1:0.33~$\pm$~0.11:0.23~$\pm$~0.08 & 20 $\pm$
      10 & \textit{COBE}/DIRBE\\ & & & & & & surface brightness map\\
      \citet{Binney1997} & & 1.9 & 100 & 1:0.6:0.4 & 20 &   \textit{COBE}/DIRBE\\
      & & & & & & surface brightness map\\
      \citet{Feast1997a} & 8.1 $\pm$ 0.4 & & & & & RR~Lyrae stars\\ 
      \citet{Stanek1997} & & & & 1:0.43:0.29 & 20--30 & red clump stars\\
      \citet{Freudenreich1998} & & 2.6 & & & & DIRBE full-sky surface\\
      & & & & & & brightness map\\
      \citet{Paczynski1998} & 8.4 $\pm$ 0.4 & & & & & red clump  stars\\
      \citet{Udalski1998} & 8.1 $\pm$ 0.15 & & & & & RR~Lyrae stars\\
      \citet{Udalski1998} & 8.1 $\pm$ 0.06 & & & & & red clump stars\\
      \citet{Sevenster1999a} &  & 2.5 & & & 44 & OH/IR stars \\  %OASP ?
      \citet{Bissantz2002}  & & 2.8 & 100 & 1:(0.3--0.4):0.3 & 20--25 & 
      \textit{COBE}/DIRBE\\ & & & & & & $L$-band map\\
      \citet{Eisenhauer2003} & 7.94 $\pm$ 0.42 & & & & & stars  orbiting black hole\\
      \citet{Robin2003} & & & & 1:0.27:0.27 & 11.1 $\pm$ 0.7 &  Hipparcos data \\
      \citet{Merrifield2004} & & & & 1:0.6:0.4 & 25 & \ion{H}{i} gas  and \textit{COBE}/DIRBE\\
      & & & & & & surface brightness map \\
      \citet{Babusiaux2005} & 7.7 $\pm$ 0.15 & & & & 22 $\pm$ 5.5 &  red clump stars\\
      \citet{Eisenhauer2005} & 7.62 $\pm$ 0.32 & & & & & stars  orbiting black hole\\
      \citet{Groenewegen2005} & 8.8 $\pm$ 0.4 & & & & 47 & Mira variables\\
      \citet{Lopez-Corredoira2005} & & & & 1:0.5:0.4 & 20--35 & 2MASS star counts \\
      \citet{Nishiyama2006} & 7.51 $\pm$ 0.10 $\pm$ 0.35 & & & & & red  clump stars\\
      \citet{Lopez-Corredoira2007} & & & & & 43 & red clump stars \\
      \citet{Rattenbury2007} & & & & 1:0.35:0.26 & 24--27 & red clump stars\\
      \citet{Ghez2008} & 8.0 $\pm$ 0.4 & & & & & stars orbiting black hole\\
{\citet{Gillessen2009} } & {8.33 $\pm$ 0.35 } & & & & & {stars orbiting black hole } \\
      \hline
    \end{tabular}} 
  \end{table}