To eliminate possible confusion in the reporting of isotopic abundances on noncorresponding scales, the Commission on Atomic Weights and Isotopic Abundances recommended at the 37(th) General Assembly at Lisbon, Portugal that (i) H-2/H-1 relative ratios of all substances be expressed relative to VSMOW (Vienna Standard Mean Ocean Water) on a scale such that H-2/H-1 Of SLAP (Standard Light Antarctic Precipitation) is 0.572 times that of VSMOW, (ii) C-13/C-12 relative ratios of all substances be expressed relative to VPDB (Vienna Peedee belemnite) on a scale such that C-13/C-12 of NBS 19 carbonate is 1.00195 times that of VPDS, and (iii) O-18/O-16 ratios of all substances be expressed relative to either VSMOW or VPDB on scales such that O-18/O-16 of SLAP is 0.9445 times that of VSMOW.