@article{HamannHeberJeffrey1996,
  author    = {Hamann, Wolf-Rainer and Heber, Ulrich and Jeffrey, C. S.},
  title     = {Wolf-Rayet stars of high and low mass},
  year      = {1996},
  language  = {en}
}
@article{HamannJeffreyLeuenhagen1996,
  author    = {Hamann, Wolf-Rainer and Jeffrey, C. S. and Leuenhagen, U.},
  title     = {Spectral analyses of late type central stars of planetary nebulae},
  year      = {1996},
  language  = {en}
}