Primary Information Source(s):

    1987 Economic Censuses CD-ROM Volume 2:  ZIP Code
    Statistics, Release 2B [machine readable data files] /
    prepared by the Bureau of the Census.     
    Washington:  The Bureau [producer and distributor], 1992.

    1987 Economic Censuses CD-ROM Volume 2:  ZIP Code
    Statistics, Release 2B Technical Documentation / 
    prepared by the Bureau of the Bureau of the Census.     
    Washington:  The Bureau, 1992.