1. Orban, B., Oral Histology and Embryology. (St. Louis, C. V. Mosby Co.: 1944) p. 104.
2. Noyes, F.B., Schour, I., AND Noyes, H.J., Dental Histology and Embryology. (Phila., Lea & Febiger: 1938) pp. 134-35.
3. Meyer's Normal Histology and Histogenesis of the Human Teeth and Associated Parts. Translated by H. R. Churchill (Phila., J. P. Lippincott Co.: 1935) pp. 57-67.
4. The Sheath of Neumann