APA

United States, . (1990). City employment: 1990. Washington: Bureau of the Census.

Chicago

United States, . 1990. City employment: 1990. Washington: Bureau of the Census.

Harvard

United States, . (1990). City employment: 1990. Washington: Bureau of the Census.

MLA

United States, . City employment: 1990. Washington: Bureau of the Census. 1990.