@book{36699,
	author = {Gregg, Michael B.},
	title = {Field epidemiology},
	publisher = {Oxford University Press,},
	year = {2008.},
	address = {New York ;},
	edition = {3rd ed.},
	url = {http://dx.doi.org/10.1093/acprof:oso/9780195313802.001.0001}
}