1. 1UnionInternationaleContreLeCancer(1974 ) TNM Classification of Malignant Tumours. Geneva.
2. 2Galen(1823 ) Opera Omnia , Vol. III , pp.525 , 525 , 525 &525 . C. G. Kuhn Ed.Leipsig.
3. 3A. Koeliker(1854 ) InManual of Human Histology , Vol. 2 , p. 162 . Sydenham Society, London.
4. 4G. Stricker(1872 ) InManual of Human and Comparative Histology , Vol. 2 , p. 38 . New Sydenham Society, London.
5. 5J. C. B. Grant(1947 ) Cunningham's Textbook of Anatomy, p. 666 , Eighth edition . Cumberledge, Oxford.