author={Fujun Du and Edwin Anthony Bergin and Michiel R. Hogerheijde},
  journal={The Astrophysical Journal Letters},
An abundance decrease in carbon- and oxygen-bearing species relative to dust has been frequently found in planet-forming disks, which can be attributed to an overall reduction of gas mass. However, in the case of TW Hya, the only disk with gas mass measured directly with HD rotational lines, the inferred gas mass ( ≲ 0.005 ?> solar mass) is significantly below the directly measured value ( ≳ 0.05 ?> solar mass). We show that this apparent conflict can be resolved if the elemental abundances of… 

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