¹⁶O/¹⁸O vs. ¹⁴N/¹⁵N ratios, both normalized by the ¹²C/¹³C ratio, for various astronomical sources. Our result for MA0.68 is in red, as is MA0.89 (MA), starburst galaxies are magenta stars (SB), Galactic sources are green triangles (MW), and the predictions from chemical evolution models in the solar neighborhood by Kobayashi et al. (2011) are in blue and labeled as S_X, where X denotes the metallicity [Fe/H]. Their models for the bulge (B) and thick disk (TD), also in blue, are for [Fe / H] = −0.5 ².