Roche, Alex F., Jean Roberts, and Peter V. V. Hamill. <i>Skeletal Maturity of Youths 12-17 Years: Racial, Geographic Area, and Socioeconomic Differentials, United States, 1966-1970.</i> Hyattsville, Md.: U.S. Department of Health, Education, and Welfare, Public Health Service, National Center for Health Statistics, 1978.