Comparison between abundances in NGC 3521 based on fibre measurements here and abundances based on H II regions from Grasha et al. (2022). Panela: Radial oxygen abundance distribution. The grey circles denote the R calibration-based abundances for the individual H II regions from Grasha et al. (2022), the red crosses denote the median values of the oxygen abundances in bins of 0.5 kpc in radius, and the bars show the scatter in O/H around the median value of each bin. The blue circles denote the median values of the oxygen abundances in bins for our fibre measurements, the line shows the O/H – R relation for those data (the same as in Fig. 4). Panelb: Same as panel (a), but for the nitrogen abundances.