Gould, J. (1873). Grey Wagtail, Calobates sulphurea [Pl. 6-7]. Zenodo.
Cita Chicago (17th ed.)Gould, John. Grey Wagtail, Calobates Sulphurea [Pl. 6-7]. Zenodo, 1873.
Cita MLA (9th ed.)Gould, John. Grey Wagtail, Calobates Sulphurea [Pl. 6-7]. Zenodo, 1873.
Atenció: Aquestes cites poden no estar 100% correctes.