1. Archer , G. F. and Godman , E. M. 1937. 1961. The Birds of British Somaliland and the Gulf of Aden. Vols 1 & 2, London: Gurney & Jackson (1937). Vols 3 & 4, London: Oliver & Boyd (1961). 4 vols.
2. Friedmann , H. 1930. 1937. Birds collected by the Child Frick Expedition to Ethiopia and Kenya Colony. Bull. U.S. natn. Mus. (Smith. Inst.) 153: parts 1 & 2.
3. Hall , B. P. and Moreau , R. E. 1970.An altas of speciation in African Passerine BirdsXV + 423London: British Museum. (Nat. Hist.). pp.
4. Mackworth-Praed , C. W. and Grant , C. H. B. 1952. London: Longmans, Green & Co. 1955. Birds of Eastern and North Eastern Africa. Vols 1 & 2. 2 vols.