References 1.L. Carlos Junqueira, Jose Carneiro, Robert O. Kelley. Basic Histology. 7th Ed. Prentice-Hall International Inc., USA. 1992.2.Michael H. Ross, Gordon I. Kaye, Wojciech Pawlina. Histology a Text and Atlas with Cell and Molecular Biology. 4th Ed. Lippincott Williams&Wilkins, USA. 2003.3.Victor P. Eroschenko. Atlas of Histology with Functional Correlations. 10th Ed. Lippincott Williams&Wilkins, USA. 2005.