@article{SteidelWallschlaegerHelb1998,
  author    = {Steidel, Gunnar and Wallschl{\"a}ger, Hans-Dieter and Helb, Hans-Wolfgang},
  title     = {Beziehungsgef{\"u}ge der Kurzstrohen des Karmingimpels (Carpodacus erythrinus) im mitteleurop{\"a}ischen Expansionsgebiet},
  year      = {1998},
  language  = {de}
}
@article{HelbWallschlaeger1996,
  author    = {Helb, Hans-Wolfgang and Wallschl{\"a}ger, Hans-Dieter},
  title     = {Geographical variation of the song of the scarlet rosefinch Carpodacus erythrinus},
  year      = {1996},
  language  = {en}
}
@article{HelbWallschlaeger1996,
  author    = {Helb, Hans-Wolfgang and Wallschl{\"a}ger, Hans-Dieter},
  title     = {Geographische Variation der Gesangsstruktur des Karminigimpels (Carpodacus erythrinus)},
  year      = {1996},
  language  = {de}
}
@article{WallschlaegerHelb1994,
  author    = {Wallschl{\"a}ger, Hans-Dieter and Helb, Hans-Wolfgang},
  title     = {Geographic variation in the scarlet grosbeak : research notes on avian biology},
  year      = {1994},
  language  = {en}
}