U.S. Census Bureau, U.S. Census of Population:
1960 and 1970;
1980 Census of Population, Vol. 1, Chapter A (PC80-1-A-1), U.S. Summary,
1990 Census of Population and Housing (CPH1); and
unpublished data.
INTERNET LINK
http://www.census.gov/population/www/
referenced on dataset section Data (#1)
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