\begin{table}%t4
%\centering
\par
\caption{\label{tab:circqso}Radio to optical polarization characteristics of objects with detected optical circular polarization.}
\par
\begin{tabular}{lcccr}
\hline\hline\noalign{\smallskip}
\multicolumn{5}{l}{1256$-$229~(PKS) $z =0.481$} HPQ, BL Lac?\\ 
\hline 
Date  &  $\nu$ (Ghz) &  $p_{\rm lin}$ (\%) &  $\theta_{\rm lin}$ ($\degr$) &  $p_{\rm circ}$ (\%)\\ 
\hline \noalign{\smallskip}
03/2002 &  $5.4\times 10^5$ &  22.32 $\pm$ 0.15 & 157 $\pm$  1\tablefootmark{d} & $-$ \ \    \\ 
04/2007 &  $5.4  \times 10^5$ &  15.42 $\pm$ 0.16 & 163 $\pm$  1\tablefootmark{j} & 0.18 $\pm$ 0.04\tablefootmark{j} \\
\hline 
\multicolumn{5}{l}{2155$-$152~(PKS) $z=0.672$}   HPQ \\ 
\hline 
Date &  $\nu$ (Ghz) &  $p_{\rm lin}$ (\%) &  $\theta_{\rm lin}$ ($\degr$) &  $p_{\rm circ}$ (\%)\\ 
\hline \noalign{\smallskip}
08/1984 & $5.4\times 10^5$ & 32.70 $\pm$ 1.30 & 6 $\pm$  1\tablefootmark{a} &  $-$ \ \     \\
04/2007 &  $5.4 \times 10^5$  &  17.67 $\pm$ 0.49 &  51 $\pm$  1\tablefootmark{j} & $-$0.35 $\pm$ 0.10\tablefootmark{j}\\
09/2007 & 85.6 &  11.04 $\pm$ 0.53 &  52 $\pm$  1\tablefootmark{i} &  $<$0.93\tablefootmark{i}\\
03/2003 &        15.4 &  3.66  & $-$\tablefootmark{f} &  $<$0.34\tablefootmark{f}    \\
1979--1999 &       8.0 &  4.81 (mean)  & $-$\tablefootmark{h} &  $-$\\
&           &  15.3 (max) & $-$\tablefootmark{h} &  $-$  \\
\hline 
\multicolumn{5}{l}{0219$+$428~(3C66A) $z =0.444$} BL Lac  \\ 
\hline 
Date &  $\nu$ (Ghz) &  $p_{\rm lin}$ (\%) &  $\theta_{\rm lin}$ ($\degr$) &  $p_{\rm circ}$ (\%)\\ 
\hline \noalign{\smallskip}
01/1992 &  $5\times 10^5$~[w] &  31.07 $\pm$ 0.31 &  39 $\pm$  1\tablefootmark{b} & 0.76 $\pm$ 0.10\tablefootmark{b}\\
12/1999 &  $5\times 10^5$~[w] &  26.11 $\pm$ 0.19 &  3 $\pm$  1\tablefootmark{c} & 0.16 $\pm$ 0.05\tablefootmark{c}\\
11/2008 &      85.6 &   4.36 $\pm$ 0.54 &  3 $\pm$  4\tablefootmark{i} &  $<$0.73\tablefootmark{i}    \\
12/1996 & 5.0 &  2.9  & $-$\tablefootmark{e} &  $<$0.20\tablefootmark{e}   \\
1974--1999 &     8.0 &  2.96 (mean)  & $-$\tablefootmark{g} &  $-$ \\
\hline 
\end{tabular}
\tablefoot{Multi-color measurements in references~($b$) and~($c$)
were averaged; upper limits are given at 3$\sigma$. References for
linear or circular polarization: 
\tablefoottext{a}{Brindle et~al. (\cite{BRI86});} 
\tablefoottext{b}{Takalo \& Sillanp\"a\"a (\cite{TAK93});} 
\tablefoottext{c}{Tommasi et~al. (\cite{TOM01b});} 
\tablefoottext{d}{Sluse et~al. (\cite{SLU05});} 
\tablefoottext{e}{Homan et~al. (\cite{HOM01});} 
\tablefoottext{f}{Homan \& Lister (\cite{HOM06});} 
\tablefoottext{g}{Fan et~al. (\cite{FAN06});} 
\tablefoottext{h}{Fan et~al. (\cite{FAN08});} 
\tablefoottext{i}{Agudo et~al. (\cite{AGU10});}
 \tablefoottext{j}{this work. }}
\end{table}