Close binary EHB stars from SPY
  We present the results of a radial velocity (RV) survey of 46 subdwarf B (sdB) and 23 helium-rich subdwarf O (He-sdO) stars. We detected 18 (39%) new sdB binary systems, but only one (4%) He-sdO binary. Orbital parameters of nine sdB and sdO binaries, derived from follow-up spectroscopy, are presented. Our results are compared with evolutionary scenarios and previous observational investigations. 
R. Napiwotzki, C.A. Karl, T. Lisker, U. Heber, N. Christlieb, D.   Reimers, G. Nelemans, D. Homeier