Hydrogen-deficient central stars of planetary nebulae

V348sgr may be more closely related to about twenty hydrogen-deficient central stars of planetary nebulae which have similar carbon abundances ($\sim10\%$) and strong emission line spectra ([Leuenhagen et al. 1995], [Leuenhagen & Hamann 1997]). These stars are all overluminous and have strong stellar winds, which give rise to Wolf-Rayet tpe spectra. Hydrogen-deficient and carbon-rich knots are seen in the inner nebulae of at least two objects (Abell 30 and Abell 78). Such knots may form in the stellar winds and from time to time give rise to RCB behaviour ([Lawson & Jones 1992]).