1. Berry , R. J. Porteus , S. D. 1920 Intelligence and social valuation . Vineland Training School Publications No. 20
2. Ring chromosome 18 in mother and daughter;Christensen;J. ment. Defic. Res.,1970
3. IgA deficiency associated with partial deletion of chromosome 18;Feingold;J. clin. Invest.,1968
4. IgA absence associated with a ring-18 chromosome;Finley;Lancet,1968