1. Oral histology: Development, structure, and function. 5th edition. St. Louis: Mosby; 1998. p 95.
2. Orban's oral histology and embryology. 10th edition. St. Louis: Mosby; 1986. pp 24-26.
3. Development of the human dentition: An atlas. Hagerstown, MD: Harper and Row; 1976. pp 284-286.