1. Al-Zahaby, S. A., & Elsheikh, E. H. (2014). Ultramorphological and histological studies on the tongue of the common kingfisher in relation to its feeding habit. The Journal of Basic and Applied Zoology, 67, 91–99.
2. Bancroft, J. D., & Stevens, A. (1996). Theory and practice of histological techniques, (4th ed., ). Edinburgh: Churchill Livingstone.
3. Bang, B.G. and Wenzel, B.M. (1995). Nasal cavity and olfactory system. In: King, A. S. and McLelland, J.( eds), Form and function in birds, (Vol. 3, Ch. 4 ,p.195-225). Academic Press, San Diego.
4. Bout, R. G., & Zweers, G. A. (2001). The role of cranial kinesis in birds. Comparative Biochemistry and Physiology, Part A, 131, 197–205.
5. El-Bakary, N. E. R. (2011). Surface morphology of the tongue of the hoopoe ( UpupaEpops). Journal of American Science, 7(1), 394–399.