\begin{table}%t2
\par
\caption{\label{tabla-d}Deuterium observational abundances $(Y_{\rm D}^{\rm obs})$.}
%\centering
\par
\begin{tabular}{lc}
\hline \hline \noalign{\smallskip}
$Y_{\rm D}^{\rm obs} \pm \sigma_{\rm D}^{\rm obs}$ & Refs.  \\ \hline
$\left (1.60^{+0.25}_{-0.30}\right ) \times 10^{-5}$ &\citet{crighton04}\\
$\left (2.42^{+0.35}_{-0.25}\right ) \times 10^{-5}$ &\citet{kirkman03}\\
$\left (3.30 \pm 0.30\right ) \times 10^{-5}$ &\citet{burles98a}\\
$\left (3.98 ^{+0.59}_{-0.67}\right ) \times 10^{-5}$ &\citet{burles98b}\\
$\left (2.54 \pm 0.23\right ) \times 10^{-5}$ &\citet{omeara01}\\
$\left (2.82^{+0.20}_{-0.19}\right ) \times 10^{-5}$ &\citet{omeara06}\\
$\left (1.65 \pm 0.35\right ) \times 10^{-5}$ &\citet{pettini01}\\
$\left (2.81 \pm 0.20\right ) \times 10^{-5}$ &\citet{pettini08}\\
$(3.75 \pm 0.25)\times 10^{-5}$ &\citet{levshakov02} \\
$3.6_{-1.1}^{+1.9} \times 10^{-5}$ &\citet{ivanchik10} \\\hline
\end{tabular}
\end{table}