\begin{table}%[h]%t1
%\scriptsize
\caption{Major blazar surveys.\label{tab1}}
%%\begin{center}
\par
\small%\centerline
{
\begin{tabular}{lllcc}
\hline\hline
 %               &   &          &      &  \\
{Survey name}   & Blazar type  &Survey type  &  Number  & Reference \\
                &              &             &  of objects &  \\
\hline
%                &   &          &      &  \\
  2 Jansky       & BL Lacs+FSRQs  &  radio flux limited  & 60 & 1, 2, 3 \\
                &                &  $F(2.7~{\rm GHz}) >$ 2 Jy, $\alpha_r \le 0.4$ & &  \\ 
  1 Jansky       & BL Lacs  &  radio flux limited & 34 & 4 \\
                &          & $F(5~{\rm GHz}) >$ 1 Jy, $\alpha_r \le 0.5$ & & \\ 
 1 Jy NVSS-RASS  & BL Lacs+FSRQs& radio, opt, X-ray selection &  157 & 5 \\
                &              & radio fl. limited, $F(1.4~{\rm GHz}) >$ 1 Jy  &                    &  \\
 1 Jy WMAP       & BL Lacs+FSRQs& microwave flux limited &180 & 6, 7 \\
                &              & $F(61~{\rm GHz}) \gtrsim$ 1 Jy     & &  \\  %\gsim$ 
 Parkes 0.25 Jy & BL Lacs+FSRQs& radio flux limited&371    & 8, 9 \\
                &              & $F(2.7~{\rm GHz}) >$ 0.25 Jy           &                    &  \\
 EMSS           & BL Lacs  &   X-ray flux limited & 41 & 10, 11 \\
                &          & $F_{X} \gtrsim 2\times 10^{-13}$ \ergs  &                    &  \\  %\gsim 
 IPC slew survey& BL Lacs  & X-ray flux limited   &  51& 12   \\
                &          & $F_{X} \gtrsim 2\times 10^{-12}$ \ergs &                    &  \\ %\gsim
 DXRBS          & BL Lacs+FSRQs&radio+opt+X-ray selection &  227 & 13, 14  \\
                &              & radio fl. limited &                    &  \\
                &                & $F(5~{\rm GHz}) > $ 50 mJy & &  \\ 
  REX            & BL Lacs      & radio+opt+X-ray selection & $\sim$100  & 15, 16  \\
%               &              &             &                    &  \\
 RGB            & BL Lacs      & radio+opt+X-ray selection   & 127  & 17 \\
%               &              &             &                    &  \\
 Sedentary      & extreme BL Lacs &radio+opt+X-ray selection&  150   & 18, 19 \\
                &              &radio fl. limited  &  &  \\
                &              & $F(1.4~{\rm GHz}) >$ 3.5 mJy  &           &  \\
 CLASS          & BL Lacs+FSRQs& radio+opt &   147 & 20, 21 \\
                &              & $F(5~{\rm GHz}) >$ 30 mJy, $\alpha_r \le 0.5$ &  &  \\
 Gamma-ray Blazars & BL Lacs+FSRQs & radio+X-ray selection &  241 & 22 \\
%               &   &          &      &  \\
 2dF BL Lac Survey & BL Lacs  & Optical selection &  56 candidates & 23, 24  \\
%               &   &          &      &  \\
 SDSS BL Lac Survey & BL Lacs  & Optical selection &  347 & 25 \\
  ROXA            & BL Lacs+FSRQs+AGN & radio+opt+X-ray selection   & 816  & 26 \\
  CGRaBS          & BL Lacs+FSRQs+AGN & radio flux limited & 1625  & 27 \\
 SDSS-FIRST BL Lac Survey  & BL Lacs   & Optical+radio selection & 501  & 28 \\
  %             &   &          &      &  \\
\hline
\end{tabular}}
%%\end{center}
\par
\smallskip
\scriptsize
(1) Wall and Peacock (1985), 
(2) di Serego-Alighieri et al. (1994),  
(3) Urry, Padovani (1995), 
(4) Stickel et al. (1991), 
(5) Giommi et al. (2002), 
(6) Bennett C.L. et al. (2003) 
(7) Giommi, Colafrancesco, (2004),
(8) jackson et al. (2002),  
(9) Wall et al. (2005),  
(10) Stocke et al. (1991),
(11) Rector et al. (2000),
(12) Perlman et al. (1996),
(13) Perlman et al. (1998), 
(14) Landt et al. (2001), 
(15) Caccianiga et al. (1999),
(16) Caccianiga et al. (2002a),  
(17) Laurent-Muehleisen et al. (1998),
(18) Giommi, Menna, Padovani (1999), 
(19) Giommi et al. (2005),
(20) March\~a et al. (2001), 
(21) Caccianiga et al. (2002b), 
(22) Sowards-Emmerd et al. (2005), 
(23) Londish et al. (2002), 
(24) Londish et al. (2007),
(25) Collinge et al. (2005),
(26) Turriziani et al. (2007),
(27) Healey et al. (2008),
(28) Plotkin et al. (2008).
\end{table}