These appear to be Census of Population and Housing, 1970 
Summary Statistic File 4A:  Housing

ICPSR Summary:

These data are from the 20-, 15-, and 5-percent samples of 
the 1970 United States Census of Population and Housing, and 
contain tabulations of housing characteristics such as 
housing value, number of housing units in structure, number 
of rooms in housing unit, year structure was built, 
occupancy/vacancy status, tenure, rent, type of heating fuel, 
source of water, and presence of an air conditioner and 
other home appliances. The unit of observation for these data 
files is the census tract. There is one file for each of 48 
states and the District of Columbia. The Census Bureau did 
not issue data for Vermont and Wyoming because these two 
states were not tracted in 1970.

jroth@nber.org
16 May 2001

cb9014.txt -- pdftotext conversion of cb9014.pdf.  Went okay.
--

Vermont and Wyoming were untracted in the 1970 census, and are not included
in this dataset.

feenberg@nber.org
17 June 1997

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http://www.census.gov/prod/www/abs/decennial/1970cenpopapo.htm
has Alphabetical Index of Industries and Occupations.