Vital and health statistics: Series 21, Data from National Vital Statistics System. 1. Natality statistics analysis, United States, 1962, analytical study of fertility trends in terms of period and cohort measures, also, discussion of characteristic of live birth including plurality, seasonal variation, period of gestation, weight at birth, sex ratio, attendant at birth, and legitimacy; [by Anders S. Lunde, Louise M. Okada, and Harry M. Rosenberg].