\begin{table}%t8
\caption{\label{tab:abundn}Relative abundances $n_{\xi} / n_{{\rm b}}$ of nitrogen species at redshifts $z=1000$, $z=100$ and $z=10$ in the SBBC (left), NSBBC1 (middle) and NSBBC2 (right) models.}
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\par
\begin{tabular}{l l l l l l l l l l}
\hline
\hline
& & SBBC & & & NSBBC1 & & & NSBBC2 &\\
\hline
Species & $z=1000$ & $z=100$ & $z=10$ & $z=1000$ & $z=100$ & $z=10$ & $z=1000$ & $z=100$ & $z=10$\\
\hline\noalign{\smallskip}
$[{\rm N}]$ & $2.3 \times 10^{-16}$ & $2.3 \times 10^{-16}$ & $2.3 \times 10^{-16}$ & $2.5 \times 10^{-16}$ & $2.5 \times 10^{-16}$ & $2.5 \times 10^{-16}$ & $3.4 \times 10^{-14}$ & $3.4 \times 10^{-14}$ & $3.4 \times 10^{-14}$\\
$[{\rm N}^+]$ & $1.1 \times 10^{-20}$ & $8.1 \times 10^{-22}$ & $6.8 \times 10^{-22}$ & $1.1 \times 10^{-20}$ & $8.6 \times 10^{-22}$ & $7.2 \times 10^{-22}$ & $1.6 \times 10^{-18}$ & $1.2 \times 10^{-19}$ & $1.0 \times 10^{-19}$\\
$[{\rm NH}]$ & $2.9 \times 10^{-30}$ & $3.4 \times 10^{-27}$ & $3.4 \times 10^{-25}$ & $3.1 \times 10^{-30}$ & $3.6 \times 10^{-27}$ & $3.7 \times 10^{-25}$ & $4.4 \times 10^{-28}$ & $5.0 \times 10^{-25}$ & $5.1 \times 10^{-23}$\\
$[{\rm NH}^+]$ & $5.4 \times 10^{-31}$ & $1.6 \times 10^{-26}$ & $2.1 \times 10^{-27}$ & $5.7 \times 10^{-31}$ & $1.7 \times 10^{-26}$ & $2.3 \times 10^{-27}$ & $8.1 \times 10^{-29}$ & $2.4 \times 10^{-24}$ & $3.2 \times 10^{-25}$\\
$[{\rm NH}_2]$ & $5.8 \times 10^{-44}$ & $3.4 \times 10^{-39}$ & $5.2 \times 10^{-35}$ & $6.2 \times 10^{-44}$ & $3.6 \times 10^{-39}$ & $5.6 \times 10^{-35}$ & $8.8 \times 10^{-42}$ & $5.1 \times 10^{-37}$ & $7.9 \times 10^{-33}$\\
$[{\rm NH}_2^+]$ & $2.1 \times 10^{-42}$ & $1.1 \times 10^{-31}$ & $5.3 \times 10^{-33}$ & $2.3 \times 10^{-42}$ & $1.2 \times 10^{-31}$ & $5.8 \times 10^{-33}$ & $3.3 \times 10^{-40}$ & $1.6 \times 10^{-29}$ & $8.1 \times 10^{-31}$\\
\hline
\end{tabular}
\end{table}