\begin{table}%T5 
\caption{\label{tab5}Yearly-averaged and period-averaged variations in the
integral Balmer decrement (BD) and continuum fluxes. } \small%\centerline
{
\begin{tabular}{lcccc}
\hline
\hline\noalign{\smallskip}
 Year     &     \multicolumn{2}{l}{$F$(H$\alpha$)/$F$(H$\beta$$)\pm \sigma$} &
\multicolumn{2}{l}{$F$(5100$)\pm \sigma$$^a$}   \\
\hline
 1996      &           3.65 & 0.51 &  11.18 & 1.55   \\
 1997      &           3.39 & 0.36 &   7.62 & 1.03   \\
 1998      &           3.58 & 0.35 &   6.08 & 1.19   \\
 1999      &           4.49 & 0.74 &   5.12 & 1.62   \\
 2000      &           5.01 & 0.62 &   2.75 & 1.33   \\
 2001      &           5.43 & 1.07 &   1.87 & 0.47   \\
 2002      &           3.67 & 0.44 &   3.59 & 0.29   \\
 2003      &           3.16 & 0.27 &   4.84 & 0.58   \\
 2004      &           3.70 & 0.29 &   2.44 & 0.57   \\
 2005      &           3.96 & 0.54 &   1.99 & 0.18   \\
 2006      &           3.58 & 0.36 &   2.60 & 0.80   \\
\hline
mean (1996--1998):    & 3.54 & 0.13 &   8.29 & 2.62  \\
\hline
mean 1999(Jan.--Apr.):& 4.21 & 0.59 &   5.89 & 0.56  \\
1999 (Dec.):         & 5.33 &      &   2.78 & 0.12  \\
\hline
mean (2000--2001):    & 5.22 & 0.30 &   2.31 & 0.62  \\
\hline
mean (2002--2006):    & 3.61 & 0.29 &   3.09 & 1.14  \\
\hline
\end{tabular}}
\smallskip
$^a$ In units of $10^{-14} \;\rm erg ~ cm^{-2}~s^{-1}~\AA^{-1}$.\\
Columns: 1 -- year
or yearly-intervals; 2 -- $F$(H$\alpha$)/$F$(H$\beta$), H$\alpha$ and
H$\beta$ flux ratio or integrated Balmer Decrement (BD); 3 --
$\sigma$($F$(H$\alpha$)/$F$(H$\beta$)), the estimated
$F$(H$\alpha$)/$F$(H$\beta$) error; 4 -- $F$(5100), continuum flux at~$\lambda 5100~\AA$; 5 -- $\sigma$, estimated continuum flux error.
The last four lines provide the mean BD, mean continuum flux, and
their estimated errors in year-periods. 
\end{table}