@inbook {9941,
	title = {Causal Inference in Sociological Studies},
	booktitle = {Handbook of Data Analysis},
	year = {2004},
	publisher = {Sage Publications},
	organization = {Sage Publications},
	address = {London},
	url = {http://www.sagepub.com/books/Book209824},
	author = {Christopher Winship and Michael Sobel},
	editor = {Melissa Hardy and Alan Bryman}
}
