1. Friedmann, H. (1930a): The caudal molt of certain coraciiform, coliiform and piciform birds. — Proc. U.S. Nat. Museum 77, Art. 7.
2. - (1930b): Siehe Lit. zu Allg. Teil.
3. Miller, W. de W. (1924): Further notes on ptilosis. — Bull. Amer. Mus. Nat. Hist. 50, p. 305–331.
4. Moreau, R. E., A. C. Wilk & W. Rowan (1948): Siehe Lit. zu Allg. Teil.
5. Murie, J. (1872): On the genusColius, its structure and systematic place. — Ibis 1872, p. 262–279.