@misc{Ruggles2004,
author = {Ruggles, S. and Sobek, M. and Alexander, T. and Fitch, C.A. and Goeken, R. and Hall, P.K. and King, M. and Ronnander, C. },
title= {Integrated public use microdata series: Version 3.0},
year = {2004},
URL = {http://usa.ipums.org/usa/},
publisher = {Minneapolis, MN: Minnesota Population Center},
}