@misc{U.S. Census Bureau2003a,
author = {U.S. Census Bureau},
title= {2000 Census. 5-Percent Public Use Microdata Sample (PUMS) Files},
year = {2003a},
URL = {http://www2.census.gov/census_2000/datasets/PUMS/FivePercent/},
publisher = {U.S. Census Bureau},
address = {Washington},
}