1. thought that the third born children were more liable to cardiac malformations, but Campbell;MacMahon,1952
2. Atlas of Congenital Cardiac Disease;Abbott, M.E.,1936
3. Congenital heart disease in Ugandan children;Caddell, J.L.; Connor, D.H.;Brit. Heart_J,1966
4. Causes of malformations of the heart;Campbell, M.,1965
5. The incidence of congenital heart disease in children born in Gothenburg 1941-1950;Carlgren, L.-E.;Brit. Heart J,1959