\begin{table}%t3
%\centering
\par
\caption{\label{sources2}Physical parameters for three LBNe.}
\begin{tabular}{cccc}
\hline\hline \noalign{\smallskip}
\ion{H}{ii} region  & LBN~676 & LBN~677 & LBN~679\\
\hline\\
$EM$(pc~cm$^{-6}$) &305 &137 (233)            &255\\ 
$n_{\rm e}$(cm$^{-3}$)                                &3.3                        &1.4\tablefootmark{a}/2.2\tablefootmark{b} (2.9\tablefootmark{b})          &2.7\\
$RM_{\rm FS}$(rad\ m$^{-2}$) &280 &--150 &--155\\
$B_{\parallel}$($\mu$G) &3.7                         &--1.9\tablefootmark{a}/--3.0$^{b}$ (--2.3\tablefootmark{b}) &--2.0\\
\hline
\end{tabular}
\tablefoot{\tablefoottext{a}{is derived for a distance of 2~kpc;}
\tablefoottext{b}{is derived for a distance of 800~pc.} For LBN~677 we use the two $EM$ values derived from radio  emission and H$\alpha$ emission (see Sect.~3.4.3).}
\end{table}