Δα_OX–(Fe II/Mg II) plane for our N (stars) and W + w (triangles) sources. The radio-loud quasar J0900+4215 is shown as a circle. The Δα_OX value, as a proxy to X-ray weakness, is compared to the newly observed properties of the Mg II region and the relative intensity of the C IV emission (see colour bar at right). An increasing trend of the Fe II/Mg II ratio with increasing X-ray weakness can be seen.