Selection of 12 of the 55 sources used to verify the deep ELAIS-N1 flux density. Each source is shown in a different colour. The circles show the LoTSS Deep measurements, and the error bars show the LoLSS, GMRT 325 MHz, GMRT 610 MHz, and FIRST measurements with the associated error in the flux density scale. The lines show the derived second-order polynomial fits: log S_I(ν) = log S₀ + Alog(ν/ν₀)+Blog(ν/ν₀)², where S₀, A and B are the best-fit parameters. The line thickness shows the uncertainty in the fit.