Zoom-in on the N V P Cygni feature, where coloured lines show best-fit model spectra for various IMF variations and a single-burst (top) and continuous star formation (bottom). Data are shown in black, and grey shaded regions mark the regions ignored in spectral fitting due to nebular or interstellar absorption or emission. For a single burst, models match the N V P Cygni comparably well. For a continuous star formation, the model without binary stars and models with shallower IMFs yield poorer matches to the N V profile.