Comparison of the normalized GTC rest-UV spectrum of some of our sources with star clusters containing VMS (R136 in blue: Crowther et al. 2016; SB 179 in green: Senchyna et al. 2017; and the Sunburst cluster in red: Meštrić et al. 2023). Gray-shaded regions mark the location of the most important spectral features associated with VMS: broad emission in N IVλ1486 and He IIλ1640, and a P-Cygni line profile in N IVλ1719. Some physical properties of these systems, including M_UV, stellar mass, and metallicity, are also shown (see text for details).