1. Ahmed, M.: Long-arm deletion of 19/20 chromosomes. Lancet 1972 I, 451.
2. Aitken, J., Brunton, M., Jacobs, P. A., Price, W. H., MacColl, K.: Chromosome studies on male patients at a mental subnormality hospital. Clin. Genet. 2, 338?346 (1971)
3. Aula, P., Gripenberg, U., Hjelt, L., Leisti, J., Palo, J., von Schoultz, B., Suomalainen, E.: Two cases with a ring chromosome in group E. Acta neurol. scand. 43, Suppl. 31, 51?52 (1967).
4. Ayraud, N., Darcourt, G., d'Oelsnitz, M., Poujol, J., Lavagna, J., Capdeville, C.: Syndrome 18p-. Une nouvelle observation. Ann. G�n�t. 12, 122?125 (1969)
5. Bernard, R., Stahl, A., Giraud, F., Hartung, M., Brusquet, Y.: Encephalopathie with a complex dysmorphia and a ring chromosome in the 17?18 group. Sem. H�p. Paris (Ann. Pediat.) 42, 2129?2133 (1966).