These are some of the books I have been using while making this encyclopedia:

English books:

Title Author ISBN Description
The Clements Checklist of Birds of the World James F. Clements Cornell University Press, ISBN 0-8014-4501-9 English and scientific names of birds of the world.
The Proper Care of Cockatoos Helmut Pinter T.F.H. Publications, Inc. ISBN 0-86622-387-8 Information about Cocatoos and beautiful photos
The Handhook of Amazon Parrots Dr. A.E. Decoteau T.F.H. Publications, Inc. ISBN 0-87666-892-9 Information about Amazon parrots – many beautiful photos.

Danish books:

Title Author ISBN Description
Politikens Stuefugle bog Henning Pust Politikens Forlag, ISBN 87-567-4008-5 Description of many species but only few color photos.
Australske Parakitter Matthew M. Vriends Aschehoug Dansk Forlag ISBN 87-11-12351-6 Australian parakeets – very thorough descriptions and color photos of the most common species.
Papegøje Håndbogen Werner Lantermann Aschehoug Fakta ISBN 87-11-12182-3 Information about care and breeding. Also many nice photos.
Papegøjer Sharmila Choudhury & Adam White Quintet Publishing Ltd. ISBN 3-8290-1695-6 Danish translation of “Identifying Parrots”; contains description of several species.
Komma’s store Papegøjebog Werner Lantermann Forlaget Komma ISBN 87-7512-278-2 Information about many species and also care and breeding.
Bogen om fugle i bur og voliere David Alderton Aschehoug Fakta ISBN 87-7512-643-5 Information about some common species in aviculture