Rest-frame UV spectra of various types of O- and B-stars (Walborn et al. 1985, 1995b) drawn from the International Ultraviolet Explorer (IUE) Atlas (http://vizier.u-strasbg.fr) and that of PKS 0529-549. At the top, we show the spectrum of a strong N-line Wolf–Rayet star, WN7-A, and as one moves down the plot, the stellar spectra are of stars of progressively later types from O3 main sequence stars to a B3 main sequence star (the specific types are indicated in the legend on the right). For easier visualization, the stellar spectra have been smoothed by a Gaussian kernel and shifted upwards in increments of 0.5.