J. O. Gjershaug, O. H. Diserud, P. C. Rasmussen, and D. Warakagoda, “An overlooked threatened species of eagle: Legge’s Hawk Eagle Nisaetus kelaarti (Aves: Accipitriformes)”, Zootaxa, vol. 1792, no. 1, pp. 54–66, Jun. 2008.