Locations of EHe stars (green, Jeffery & Hamann 2010) the luminous sdO-stars (purple, Müller-Ringat 2013; Rauch et al. 1998, 1991; Husfeld et al. 1989) and O(He) stars (red, this work, Werner et al. 2014; Wassermann et al. 2010) as well as the DO WDs (black, Werner et al. 2014; Mahsereci 2011; Hügelmeyer et al. 2006; Dreizler & Werner 1996) in the log T_eff  – log g plane compared with an LTP (dashed line) and VLTP post-AGB (solid lines) evolutionary tracks (labeled with stellar masses in M_⊙) of Miller Bertolami & Althaus (2006). Open symbols indicate CSPNe, filled ones indicate that no PN was detected. C-rich objects are represented by triangles, N-rich objects by inverted triangles, C- and N-rich objects by diamonds. Squares specify objects that are neither enriched in C nor in N.