Umosen, A.D., et al. “Observations on the Wattles of Adult Helmeted Guinea Fowls (Numida Meleagris Galeata)”. International Journal of Poultry Science, vol. 7, no. 12, Nov. 2008, pp. 1204–1206, https://doi.org/10.3923/ijps.2008.1204.1206.