For the literature, see A. Newton, Dict. Birds, 1893, pp. 220-221, 303-308.
P.Z.S. 1882, pp. 312-332; Bronn's Thier-Reich, Aves, Syst. Theil, pp. 207-209.
For further details see A. Newton, Ibis, 1864, pp. 185-222; 1890, pp. 207-214; Dict. Birds, 1894, pp. 805-810; cf. also Zool. Rec. 1888-89.
Bronn's Thier-Reich, Aves, Syst. Theil, 1893, p. 210.
Cat. Birds Brit. Mus. xxi. 1893, p. 3.