These studies cover three countries and a period from 1929 to 1971.

The new study covered the period from 1985 to 1992.

The study covered the 1989-92 period, the latest for which numbers were available.

The study covered four time periods, from 1960 to 1962, 1970 to 1974, 1976 to 1980 and 1988 to 1991.

The Dutch study covered the period from 1982 to 1988.

The studies covered 188 participants, who ranged in age from 2 to 17.

The studies cover where the language originated and how it spread.

The study did not cover the situation of the single-parent family.

The study covered the period from 1979 through 1987.

The study covered the 95 senators who filed their reports earlier this week.