↑ Ferguson-Lees, James; Christie, David (2005). Raptors of the World: A Field Guide (Helm Field Guides). Christopher Helm Publishers Ltd. ISBN 0713669578.
↑ del Hoyo, J., Elliott, A., & Sargatal, J., eds. (1994). Handbook of the Birds of the World Vol. 2. Lynx Edicions, Barcelona ISBN 84-87334-15-6.
