Overview of popular molecular gas mass (﹩{M}_{\mathrm{mol}\mathrm{gas}}﹩) calibration methods for high-redshift (i.e., ﹩z\gt 1﹩) galaxies sorted into three categories: (a) (sub)millimeter emission line observations, (b) galaxy SED-fitted dust mass, and (c) RJ-tail dust continuum. See description in Section 3. The corresponding sections in this paper are labeled in the flow chart. The references for the ﹩{\alpha }_{850,\mathrm{mol}}﹩ conversion factors are Scoville et al. (2017; S17) and Hughes et al. (2017; H17); and for α_{160–500,mol}, Groves et al. (2015; G15).