http://europepmc.org/abstract/MED/19654501
http://europepmc.org/abstract/MED/20090505
http://europepmc.org/abstract/MED/18094413
http://europepmc.org/abstract/MED/17724745
http://europepmc.org/abstract/MED/18300800
http://europepmc.org/abstract/MED/17188428