RT Journal Article SR Electronic T1 Essentials of Medical Genetics JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 546 OP 546 DO 10.1136/jmg.8.4.546 VO 8 IS 4 A1 A. W. Johnston YR 1971 UL http://jmg.bmj.com/content/8/4/546.1.abstract AB