Bmc public health - research article
2009, 9:316 doi:10.1186/1471-2458-9-316 Received: 30 April 2009 Accepted: 1 September 2009 This article is available from: http://www.biomedcentral.com/1471-2458/9/316 © 2009 Di Bartolomeo et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative ...