O-Connor, R. J. The growth and development of birds. John Wiley and Sons.
Chicago-viite (17. p.)O-Connor, Raymond J. The Growth and Development of Birds. John Wiley and Sons.
MLA-viite (8. p.)O-Connor, Raymond J. The Growth and Development of Birds. John Wiley and Sons.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.