Equations for calculating delta values incorporating different H3+ values are given in: T. B. Coplen, Normalization of oxygen and hydrogen isotope data, Chem. Geol. 72, 293-297 (1988). Coplen, Wildman, and Chen, Improvements in the Gaseous Hydrogen- Water Equilibration Technique for Hydrogen Isotope Ratio Analysis, Anal. Chem., 910-912 (1991). In fact, setting the H3+ to zero is required to get the best data when analyzing urine samples for d2H by H2 equilibration using a Finnigan 251 mass spectrometer at Phoenix, National Institutes of Health (I. Harper). Calculation of final d2H is performed by off line evaluation.