\begin{table}%t1
  \caption{\label{resu}Derived upper limits on O$_2$~column density relative to~H$_2$. The 
  1~channel rms noise is given in the $T_{\rm A}$~scale,
  but all computations have been done assuming a 90\% coupling to 
the
  main beam. 
Resolution is~0.3~km$^{-1}$ except for~G0.26-0.01 (2.5~km$^{-1}$).
6.8(14) means $6.8 \times 10^{14}$. The {"Ref.''} column provides references
 for the C$^{18}$O data.} 
 $$
        \begin{array}{lr@{^{\rm h}}lr@{^\circ}lcr@{.}lr@{.}lccccr}
            \hline\hline
            \noalign{\smallskip}
  {\rm Source} &
\multicolumn{2}{c}{\alpha_{2000}}&\multicolumn{2}{c}{\delta_{2000}}&
{\rm O}_2 ~{\rm rms} & \multicolumn{2}{c}{\int T_{\rm r}^*{\scriptstyle({\rm C}^{18}{\rm O})}{\rm d}v}&
\multicolumn{2}{c}{\Delta v{\scriptstyle(C^{18}{\rm O})}} & T_{\rm {kin}} &  N({\rm O}_2)& N({\rm C}^{18}{\rm O}) &  X({\rm O}_2)& {\rm Ref.}\\
         &\multicolumn{2}{c}{}&\multicolumn{2}{c}{}&{\rm (K)}&\multicolumn{2}{c}{{\rm (K~km~s^{-1})}}&\multicolumn{2}{c}{{\rm (km~s^{-1})}}&  {\rm (K)}&         {\rm (cm^{-2})}&       {\rm (cm^{-2})}&&\\
            \noalign{\smallskip}
            \hline
            \noalign{\smallskip}
{\rm TMC1-NH_3}&    4&41^{{\rm m}}16^{{\rm s}}&   25&48\arcmin44\arcsec&  0.010&  1&6&                         1&1&     10  &  \leq\!6.8(14)  &  1.5(15)    &        \leq\!7.7(-8)  &               1\\
{\rm Orion A}& 5&35^{{\rm m}}14\fs36&-5&22\arcmin30\arcsec&  0.006&   2&7  &                        3&8 &     50 &    \leq\!1.9(15)&     3.6(15)   &           \leq\!8.9(-8) &                 2\\
{\rm NGC 2071}&5&47^{{\rm m}}4\fs1&   0&21\arcmin42\farcs8& 0.026 &  2&86  &                       1&8 &     20&     \leq\!2.6(15)&      2.8(15)   &           \leq\!1.5(-7) &                 3\\
{\rm L134N-NH_3}&15&54^{{\rm m}}08\fs52&-2&52\arcmin48\arcsec&  0.024&   1&16  &                       0&6 &     10&     \leq\!1.1(15) &     1.1(15)   &           \leq\!1.7(-7) &                 4\\
{\rm \rho Oph A}  &16&26^{{\rm m}}26\fs4& -24&24\arcmin30\farcs5&  0.027&   5&17 &                   1&53 &    30&     \leq\!3.4(15) &     6.2(15)   &           \leq\!9.3(-8) &                 5\\
{\rm IRAS16293}&16&32^{{\rm m}}22\fs8& -24&28\arcmin35\arcsec&  0.017&   2&07  &                      0&94&     30&     \leq\!1.7(15) &     2.5(15)     &         \leq\!1.2(-7)  &                5\\
{\rm NGC6334I} &17&20^{{\rm m}}53\fs38&-35&47\arcmin1\farcs5& 0.017&   30&^{{\rm a}}&   4&0 &     50 &    \leq\!5.0(15)&^{{\rm d}}&   \leq\!7.1(-8)^{{\rm e}} &  6{-}8\\
{\rm (G0.26-0.01)^{{\rm c}}}&17&46^{{\rm m}}11^{{\rm s}}&   -28&42\arcmin39\arcsec&   0.021&   11&75   &                 (164&0)^{{\rm c}} &   20 ? &   \leq\!5.6(16) &     1.2(16)   &          \leq\!7.6(-7) &               9,10\\
{\rm M17SW}    &18&20^{{\rm m}}23\fs11&-16&12\arcmin47\farcs2&  0.024&   2&84  &                     4&3&      50 &    \leq\!7.3(15) &     3.0(15)  &           \leq\!5.7(-7) &                11\\
{\rm S68 FIRS1}&18&29^{{\rm m}}50\fs3& 1&15\arcmin18\farcs6&  0.016&   2&63   &                      1&4 &     25 &    \leq\!1.6(15) &     2.8(15)  &           \leq\!9.7(-8)  &               12\\
{\rm G34.3+0.2}&18&53^{{\rm m}}18\fs34&1&14\arcmin58\farcs4&  0.021&\multicolumn{2}{l}{\hspace{0.4cm}^{{\rm b}}}&6&0 &     30 &    \leq\!5.2(15)&^{{\rm d}} &\leq\!5.2(-8) &         13{-}16\\
            \noalign{\smallskip}
            \hline
         \end{array}
    $$
 \end{table}