1. Warkany, J.: Congenital Malformations, Ist ed.Chicago: Year Book Medical Publishers. Inc., 1971.
2.
2. Stevenson, A.C., Johnson, H.A., Stewart, M.I. P. and Golding, D.R.: Congenital Malformations: A Report of a Study of Series of Consecutive Births in 24 Centers. Supplement to Vol. 31, Bulletin, World Health Organization, 1966, p. 1.
3.
3. No reference given.
4.
4. Potter, E.L.: Pathology of the Fetus and Infant, 2nd ed.Chicago: Year Book Medical Publishers, Inc., 1961, p. 224.
