\begin{table}%t2
\par
\caption{\label{table_PN}Median abundance values (number of objects).}
\par
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\hline\hline
%& \multicolumn{3}{c}{Bulge PNe} & \multicolumn{3}{c}{Arcturus} \\
               & Bulge PNe           &       & Inner-disk PNe &
& LMC PNe            &        & Bulge giants          &     &
Sun$^{a}$ & HII regions$^{b}$ \\
\hline
      $\log\epsilon$(He)     & 11.11 ~[11.05, 11.19] & (144) & 11.08 ~[11.02, 11.14] & (56)
& 11.00 [10.92, 11.07] & (99)  &  --            &            & 10.93
$\pm$ 0.01 & --\\
      $\log\epsilon$(O)      &  ~~8.57 ~~[8.40,   8.72] & (117) &  ~~8.51 ~~[8.28,   8.66] & (44)
&  ~~8.24 ~[8.05,   8.39] & (87)  &  ~8.91 ~[8.82,   9.02] & (42)  & ~8.66
$\pm$ 0.05 & -- \\
      $\log\epsilon$(Ar)     &  ~~6.34 ~~[6.05,   6.56]  & (120) &  ~~6.26 ~~[5.76,   6.50] & (49)
&  ~~5.90 ~[5.75,   6.02] & (87)  &  ~--                  &      & ~6.18
$\pm$ 0.08 & -- \\
      $\log\epsilon$(Ne)     &  ~~7.93 ~~[7.71,   8.17] & (77)  &  ~~7.91 ~~[7.61,   8.09] & (36)
&  ~~7.62 ~[7.42,   7.80] & (85)  &  ~8.22 ~[8.02,   8.31] & (48)  & ~7.84
$\pm$ 0.06 & -- \\
      $\log\epsilon$(S)      &  ~~6.79 ~~[6.54,   7.04] & (94)  &  ~~6.67 ~~[6.45,   6.98]  & (36)
&  ~~6.44 ~[6.30,   6.60] & (63)  &  ~7.08 ~[6.83,   7.31] & (23)  & ~7.14
$\pm$ 0.05 & -- \\
      $\log\epsilon$(N)      &  ~~8.11 ~~[7.76,   8.50] & (123) &  ~~7.99 ~~[7.42,   8.34] & (45)
&  ~~7.75 ~[7.35,   8.15] & (85)  &  ~8.40 ~[8.09,   8.49] & (48)  & ~7.78
$\pm$ 0.06 & -- \\
      $\log\epsilon$(Cl)     &  ~~6.22 ~~[6.00,   6.50] & (47)  &  ~~6.27 ~~[5.97,   6.63] & (19)
&  ~~5.67 ~[--,       --] & (4)   &  ~--                  &      & ~5.50
$\pm$ 0.30 & -- \\
\hline
      log~(S/O)      & $-$1.74 [$-$1.91, $-$1.59] & (127) & $-$1.79 [$-$2.03, $-$1.63] & (42)
& $-$1.79 [$-$1.99, $-$1.54] & (80)  & $-$1.64 [$-$1.78, $-$1.58] & (22)  & $-$1.52 &
$-$1.696, $-$1.739\\
      log~(Ne/O)     & $-$0.62 [$-$0.74, $-$0.52] & (90)  & $-$0.59 [$-$0.70, $-$0.48] & (46)
& $-$0.67 [$-$0.78, $-$0.52] & (99)  & $-$0.78 [$-$0.90, $-$0.64] & (64)  & $-$0.82 &
$-$0.834, $-$0.688 \\
      log(Ar/O)     & $-$2.22 [$-$2.38, $-$2.05] & (141) & $-$2.22 [$-$2.41, $-$2.08] & (51)
& $-$2.35 [$-$2.48, $-$2.13] & (96)  &  --             &           & $-$2.48 &
$-$2.441, $-$2.376\\
      log~(S/Ar)     &  ~~0.46 ~[0.31,  0.61]  & (111) &  ~~0.39 ~[0.23,  0.59] & (37)
&  ~~0.52 ~[0.39,  0.66] & (69)  &  --           &             &  ~~0.96 &
0.745, 0.637 \\
      log~(N/O)      & $-$0.39 [$-$0.68, $-$0.11] & (136) & $-$0.55 [$-$0.77, $-$0.27] & (50)
& $-$0.51 [--0.89,  ~0.00] & (85)  & $-$0.54 [$-$0.75, $-$0.45] & (42)  & $-$0.88 &
-- \\
      log~(N/Ar)     &  ~~1.86 ~[1.60,  2.05] & (138) &  ~~1.81 ~[1.51,  1.95]  & (45)
& ~ ~1.86 ~~[1.55,  2.22] & (84)  &  --       &                 &  ~~1.6  &
-- \\
\hline
\end{tabular}} 
\par
\smallskip
$^{a}$ Asplund et~al. (\cite{Asplund05});
$^{b}$ Izotov et~al. (\cite{Izotov06}).
\end{table}