Double degenerates from the supernova Ia progenitor survey (SPY)
  We report on follow-up observations of double degenerate (DD) white dwarfs from the Supernovae Ia Progenitor Survey (SPY). Orbital parameters of four systems, including a massive short period system, are presented. 
C. Karl, R. Napiwotzki, U. Heber, T. Lisker, G. Nelemans, N.   Christlieb, D. Reimers