Literature
  • Schildmacher 1982
  • Einführung in die Ornithologie. VEB Fischer Verlag, Jena. 283 pp.
  • Perremans 1990a
  • External surface structures of rachis, rami and rachidial barbules of feathers and their potential for determination purposes. 20th Meeting Bird Strike committee Europe Helsinki. Working Paper 3: 21-30.