(a) N/O abundance ratio vs. oxygen abundance for the sample of low‐metallicity blue compact galaxies (open circles) from Thuan et al. (1995) and Izotov et al. (1996b). The location of SBS 0335−052 is shown by the filled circle. The leftmost point is for I Zw 18. Note the low spread of points and absence of an apparent trend in the N/O vs. O/H diagram, implying that nitrogen is a primary element produced by massive stars. (b) Location of SBS 0335−052 in the diagram of N/O abundance ratio vs. oxygen abundance (filled circle). For comparison, the data for the sample of low‐metallicity BCGs (open circles) from Thuan et al. (1995) and Izotov et al. (1996b) are shown. (c, d) Same as (b), but for S/O and Ar/O, respectively.