Key points are not available for this paper at this time.
Melvin Zelnik, John F. Kantner, Sexual and Contraceptive Experience of Young Unmarried Women in the United States, 1976 and 1971, Family Planning Perspectives, Vol. 9, No. 2 (Mar. - Apr., 1977), pp. 55-56+58-63+67-71
Zelnik et al. (Tue,) studied this question.